Chapter 11. Networking
This chapter covers the following subjects:
Network Cable and Connector Types and Characteristics—This section defines twisted pair cable, coaxial, fiber-optic, and the different connectors each cable uses.
TCP/IP—In this section, you learn the basics about the Transmission Control Protocol/Internet Protocol (TCP/IP) suite and common protocols, the differences between IPv4 and IPv6, static vs. dynamic IP addressing, client-side DNS, and much more.
TCP and UDP Ports, Protocols, and Purposes—This section covers the concepts behind TCP and UDP ports, typical port numbers, and the protocols and features they support.
WiFi (Wi-Fi) Network and Encryption Standards—Learn the characteristics of Wi-Fi standards from 802.11b to 802.11ac, MIMO antennas, and encryption types.
Configure SOHO Wired or Wireless Router—Discover how to select the best channels, use port forwarding and DMZ, control the DHCP address range, use basic QoS and UPnP for better media playback, and improve your router with vendor-supplied and third-party firmware updates.
Internet Connection Types—This section covers the essential features of Internet connections from cable, DSL, and dial-up to fiber, satellite, ISDN, and line-of-sight wireless.
Network Types—A brief review of network types.
Network Architecture Devices—This section covers the building blocks of networks from hubs and switches to routers and repeaters.
Using Networking Tools—Learn how to choose and use the tools you need for the network types you support.
Network support is universal in computers and mobile devices of all types. There are many hardware and software components involved in connecting computers and mobile devices to each other, from cabling, connectors, and Wi-Fi radios to routers, TCP ports, and DHCP servers. This chapter helps you understand the fundamentals of wired and wireless networking.
220-901: Objective 2.1 Identify the various types of network cables and connectors.
220-901: Objective 2.2 Compare and contrast the characteristics of connectors and cabling.
220-901: Objective 2.3 Explain the properties and characteristics of TCP/IP.
220-901: Objective 2.4 Explain common TCP and UDP ports, protocols, and their purpose.
220-901: Objective 2.5 Compare and contrast various WiFi networking standards and encryption types.
220-901: Objective 2.6 Given a scenario, install and configure SOHO wireless/wired router and apply appropriate settings.
220-901: Objective 2.7 Compare and contrast Internet connection types, network types and their features.
220-901: Objective 2.8 Compare and contrast network architecture devices, their functions and features.
220-901: Objective 2.9 Given a scenario, use appropriate networking tools.
Foundation Topics
Network Cable and Connector Types and Characteristics
There are three major types of network cables:
Fiber
Twisted-pair (UTP)
Coaxial
Network cards are designed to interface with one or more types of network cables, each of which is discussed in the following sections.
Fiber
Fiber-optic cabling transmits signals with light rather than with electrical signals, which makes it immune to electrical interference. It is used primarily as a backbone between networks. Fiber-optic cable comes in two major types:
Single-mode fiber—Has a thin core (between 8 and 10 microns) designed to carry a single light ray long distances (up to 60Km or further). Single-mode cable uses a laser diode as a light source. Typical uses: cable TV and telephone companies.
Multi-mode fiber—Has a thicker core (62.5 microns) than single-mode; carries multiple light rays for short distances (up to 10Km). Multi-mode cable uses an LED light source. Typical uses: local and metropolitan area networks (LANs, MANs).
Fiber-optic cabling can be purchased prebuilt, but if you need a custom length, it should be built and installed by experienced cable installers because of the expense and risk of damage. Some network adapters built for servers are designed to use fiber-optic cable. Otherwise, media converters are used to interconnect fiber-optic to conventional cables on networks.
Fiber-optic devices and cables use one of several connector types. The most common include:
SC—Uses square connectors
LC—Uses square connectors
ST—Uses round connectors
These connectors can be used singly or in pairs, depending upon the implementation. Figure 11-1 illustrates duplex (paired) SC, LC, and ST multimode cables.
Note
If you need to interconnect devices that use two different connector types, use adapter cables that are designed to match the connector types and other characteristics of the cable and device.
Twisted-Pair
Twisted-pair (TP) cabling is the most common of the major cabling types. The name refers to its physical construction: four twisted-pairs of wire surrounded by a flexible jacket (unshielded TP or UTP) or various types of metal foil or braid (shielded TP or STP).
TP Cable Grades
TP cable comes in various grades, of which Category 5e (CAT5e), Category 6 (CAT6), and Category 6a (CAT6a) are the most common of the standard cabling grades. These are suitable for use with both standard 10BASE-T and Fast Ethernet networking and can also be used for Gigabit Ethernet networks if it passes compliance testing. CAT6, CAT6a, and Category 7 (CAT7) are capable of supporting 10GBASE-T (10 Gigabit) Ethernet networks. Table 11-1 provides the essential information about each of the TP cable types you need to know for the exam.
Shielded Twisted-Pair (STP) versus Unshielded Twisted-Pair (UTP)
STP uses the same RJ-45 connector as UTP but includes a metal shield for electrical insulation between the wire pairs and the outer jacket. It’s stiffer and more durable, but also more expensive and harder to loop through tight spaces than UTP. It is used where electromagnetic interference (EMI) prevents the use of UTP cable.
Figure 11-2 compares the construction of STP and UTP cables.
Figure 11-2 An STP cable (left) includes a metal shield and ground wire for protection against interference, while a UTP cable (right) does not.
UTP and STP cable can be purchased in prebuilt assemblies or can be built from bulk cable and connectors.
T568B (EIA-568B) and T568A (EIA-568A) Standards
The de facto wire pair standard for all types of Ethernet UTP cables is known as T568B (also known as EIA-568B). The wire order from left to right when looking at the top of the connector is:
Pin 2—Orange
Pin 3—Green/white stripe
Pin 4—Blue
Pin 5—Blue/white stripe
Pin 6—Green
Pin 7—Brown/white stripe
Pin 8—Brown
The T568A (EIA-568A) standard swaps the position of the orange and green wires used in T568B. The wire order from left to right when looking at the top of the connector is:
Pin 1—Green/white stripe
Pin 2—Green
Pin 3—Orange/white stripe
Pin 4—Blue
Pin 5—Blue/white stripe
Pin 6—Orange
Pin 7—Brown/white stripe
Pin 8—Brown
Figure 11-3 illustrates cable pairings for a T568B cable, a T568B cable with connector, and the cable pairings for a T568A cable.
You can create a crossover cable by building one end to the T568B standard and the other end to the T568A standard.
RJ-45 Versus RJ-11
The connector used by Ethernet cards that use UTP or STP cable is commonly known as an RJ-45 connector. RJ stands for registered jack; the RJ-45 has eight contacts that accept eight wires, also known as pins. It resembles a larger version of the RJ-11 connector used for telephone cabling. TP cabling runs between a computer on the network and a hub or switch carrying signals between the two. The hub or switch then sends signals to other computers (servers or workstations) on the network. When a computer is connected to a hub or switch, a straight-through cable is used. This means that both ends of the cable are wired the same way. When a computer needs to be connected directly to another computer, a crossover cable, which has a different pin configuration on one end, is used. Keep in mind that between the computer and the hub or switch, other wiring equipment might be involved, for example, RJ-45 jacks, patch panels, and so on. TP cable can be purchased in prebuilt form or as bulk cable with connectors, so you can build the cable to the length you need. Figure 11-4 compares RJ-11 and RJ-45 cables.
Note
Although RJ-45 is the common name for the TP Ethernet connector, this is a misnomer; the proper name is 8P8C (8 position, 8 contact). Don’t confuse it with the RJ-45S connector, an eight-position connector used for telephone rather than computer data. An RJ-45S jack has a slightly different shape than the connector.
Figure 11-5 compares RJ-11 and RJ-45 ports.
10BASE-T, 100BASE-T, and 1000BASE-T Ethernet cards using copper wire all use the RJ-45 connector shown in Figure 11-5, as do some ISDN and most cable Internet devices. DSL devices often use the RJ-11 connector shown in Figure 11-5, as do dial-up modems.
To attach a cable using RJ-11 or RJ-45 connectors to a network card or other device, plug it into the connector so that the plastic locking clip snaps into place; the cable and connector will fit together only one way. To remove the cable, squeeze the locking clip toward the connector and pull the connector out of the jack. Some cables use a snagless connector; squeeze the guard over the locking clip to open the clip to remove the cable.
Coaxial
Coaxial cabling is the oldest type of network cabling; its data wires are surrounded by a wire mesh for insulation. Coaxial cables, which resemble cable TV connections, are not popular for network use today because they must be run from one station directly to another rather than to or from a hub/switch. However, coaxial cabling is used for most cable TV, cable Internet, and satellite TV installations as well as CCTV cameras used for security.
Legacy 10Mbps Ethernet Coaxial Cable Standards
Coaxial cabling creates a bus topology; each end of the bus must be terminated, and if any part of the bus fails, the entire network fails.
The oldest Ethernet standard, 10BASE5, uses a very thick coaxial cable (RG-8) attached to a NIC through an AUI transceiver that uses a so-called “vampire tap” to connect the transceiver to the cable. This type of coaxial cable is also referred to as Thick Ethernet or Thicknet.
Thin Ethernet, also referred to as Thinnet, Cheapernet, or 10BASE2 Ethernet was used for low-cost Ethernet networks before the advent of UTP cable. The coaxial cable used with 10BASE2 is referred to as RG-58. This type of coaxial cable connects to network cards through a T-connector that bayonet-mounts to the rear of the network card using a BNC connector. The arms of the T are used to connect two cables, each running to another computer in the network.
If the workstation is at the end of a network, a terminating resistor is connected to one arm of the T to indicate the end of the network. If a resistor is removed, the network fails; if a station on the network fails, the network fails.
Both of these connection types are shown in Figure 11-6. Note that some 10Mbps Ethernet cards are combo cards that might feature both legacy connector types as well as, on some models, an RJ-45 jack.
Figure 11-6 Combo UTP/BNC/AUI Ethernet network cards (left and right) compared with a UTP/STP-only Ethernet card (center) and cables.
RG-59 and RG-6 Coaxial Cable
Two other types of coaxial cable are common in cable Internet, satellite Internet, and fixed wireless Internet installations:
RG-59—Used in older cable TV or satellite TV installations as well as in CCTV security installations; 75-ohm resistance. RG-59 uses a 22-gauge (AWG) center conductor and a single outer shield. It is designed for signals up to 50MHz.
RG-6—Uses same connectors as RG-59 but has a larger diameter with dual shielding; used in cable TV/Internet, satellite TV/Internet, fixed wireless Internet/TV service, and closed-circuit (security) TV; 75-ohm resistance. RG-6 uses an 18-gauge (AWG) center conductor, which can carry a signal further than RG-59. RG-6 is also available in quad-shielded versions. RG-6 can carry signals up to 1.5GHz, making it much better for HDTV signals.
BNC connectors are used for CCTV cameras and for some types of video projectors. BNC connectors are crimped to the coaxial cable and use a positive locking bayonet mount.
The F-connector is used for cable, satellite, and fixed wireless Internet and TV service. F-connectors can be crimped or attached via compression to the coaxial cable. High-quality cables use a threaded connector. However, some F-connector cables use a push-on connector, which is not as secure and can lead to a poor-quality connection. Figure 11-7 compares BNC and F-connectors on an RG-6 coaxial cable.
A two-way splitter such as the one shown in Figure 11-8 reduces signal strength by 50 percent (3.5dB) on each connection. If you split the signal only once with a high-quality signal and cables, you will usually not have issues with your TV or Internet signal. However, if you do, contact your TV or Internet provider for a splitter or ask what type of booster is recommended for your installation.
Note
Many antennas used for over-the-air digital TV now include a small in-line booster that is powered by a 500mA USB connection or a small AC adapter. The booster helps improve range and bring in more stations.
Plenum and PVC
There are three categories of TP and coaxial cable in terms of fire rating:
Standard cable suitable for patch cables between a NIC and a network jack or in a patch panel. This type of cable typically uses a PVC jacket, which can create a lot of smoke when burned.
Riser cable is stiffer and is designed for vertical cable runs. Riser cable is also suitable for use in horizontal runs such as patch cables and patch panels. In fact, some cable vendors sell only riser and plenum cables.
Plenum cable is designed for use in plenum space (space used for HVAC air exchange), such as ventilator shafts, under floors, or between suspended ceilings and the permanent ceiling. Plenum cable produces less smoke when burned, a lower level of toxic chemicals when burned, and is typically self-extinguishing. Plenum cable jackets might be made from Teflon or from a modified version of PVC that produces less smoke when burned than standard PVC.
TCP/IP
TCP/IP is short for Transport Control Protocol/Internet Protocol. It is a multiplatform protocol used for both Internet access and local area networks. Though there are other networking protocols, TCP/IP is by far the most common and is used by all major operating systems including Windows, OS X, Linux, Android, and iOS.
TCP/IP actually is a suite of protocols used on the Internet for routing and transporting information. The following sections discuss some of the application protocols that are part of the TCP/IP suite, as well as some of the services and technologies that relate to TCP/IP.
The TCP/IPv4 protocol, although it was originally used for Internet connectivity, is the main network protocol for LANs as well as larger networks; in networks today, TCP/IP v4 and v6 are used side by side. To connect with the rest of a TCP/IP-based network, each computer or other device must have a unique IP address. If the network connects with the Internet, additional settings are required.
IPv4
An IPv4 address consists of a group of four numbers that each range from 0 to 255, for example: 192.168.1.1. IP addresses are divided into two sections: the network portion, which is the number of the network the computer is on, and the host portion, which is the individual number of the computer. Using the IP address we just mentioned as an example, the 192.168.1 portion would typically be the network number, and .1 would be the host number. A subnet mask is used to distinguish between the network portion of the IP address and the host portion. For example, a typical subnet mask for the IP address we just used would be 255.255.255.0. The 255s correspond to the network portion of the IP address. The 0s correspond to the host portion, as shown in Table 11-2.
The subnet mask is also used to define subnetworks, if subnetworking is being implemented.
Both computers and other networked devices, such as routers and network printers, can have IP addresses, and some devices can have more than one IP address. For example, a router typically has two IP addresses—one to connect the router to a LAN and the other that connects it to the Internet, enabling it to route traffic from the LAN to the Internet and back.
Class A, B, and C IP Address Ranges
Traditionally, IP addresses were divided into three major categories: Class A, Class B, and Class C, which define ranges of IP addresses. Class A is designated for large corporations, ISPs, and government. Class B is designated for midsized corporations and ISPs. Class C is designated for small offices and home offices. Each class of IP address uses a default subnet mask, as shown in Table 11-3.
Note
The 127 network is reserved for testing. This is known as the IPv4 loopback address (for example, 127.0.0.1). The usable starting IP for Class A is actually 1.0.0.0.
In any given network, the first and last addresses are reserved and cannot be assigned to computers or other hosts. For example, in the 192.168.1.0 network, 192.168.1.1 through 192.168.1.254 can be assigned, but 192.168.1.0 is reserved for the network number, and 192.168.1.255 is reserved for something called the broadcast.
Each number in an IP address is called an octet. An octet is an eight-bit byte. This means that in the binary numbering system the number can range from 00000000–11111111. For example, 255 is actually 11111111 when converted to the binary numbering system. Another example: 192 equals 11000000. Because there are four octets in an IPv4 address, it is a 32-bit address. IPv4 supports up to 4.3 billion addresses (4.3×109).
Note
To convert numbers from decimal to binary and vice versa use the Windows calculator. Press Windows+R to bring up the Run prompt; then type calc. This runs the Windows Calculator. From there, click View on the menu bar and select Scientific (Vista) or Programmer (7/8/8.1/10). Now you will notice radio buttons on the upper left (Vista) or left (7/8/8.1/10) that allow you to change between numbering systems. Simply type any number, and then select the numbering system you want to convert it to.
In a Class A network, the first octet is the network portion of the IP address, and the three remaining octets identify the host portion of the IP address. Class B networks use the first and second octets as the network portion and the third and fourth octets as the host portion. Class C networks use the first three octets as the network portion and the last octet as the host portion of the IP address. Table 11-4 gives one example IP address and subnet mask for each class.
See a pattern? The size of the network portion increases in octets, and the host portion decreases as you ascend through the classes.
Using Subnetting
By changing the subnet mask from the default value, you enable a network to be subdivided into smaller networks. When you change the subnet mask, you borrow bits from the network portion and add them to the host address portion.
For example, a Class C network starting with 192.168.1.1 has a default subnet mask of 255.255.255.0, which does not subnet the network.
In binary, 255.255.255.0 is represented as 00000000 (eight zeros).
Some of the allowable subnetting values for Class C networks include:
255.255.255.128 (binary 10000000, two subnets)
255.255.255.192 (binary 11000000, four subnets)
255.255.255.224 (binary 11100000, eight subnets)
Note
For an excellent guide to subnetting, see the TCP/IP Guide’s IP Subnet Addressing (“Subnetting” Concepts) at http://www.tcpipguide.com/free/t_IPSubnetAddressingSubnettingConcepts.htm
Using CIDR
Even with subnetting enabling a single larger network to be subdivided for easier management and security, class-based IPv4 networks can still have problems with unused IP address space and problems with connecting networks with other networks. To solve these problems, classless interdomain routing (CIDR) was developed.
Instead of using subnet masks, CIDR lists networks by a prefix consisting of the starting IP address and the number of mask bits set to 1 (binary). For example, a CIDR value such as 172.168.0.1/18 represents a range of IP addresses from 172.168.0.0 to 172.168.63.255 using a subnet mask of 255.255.192.0. This translates to 16,256 addresses (equivalent to 64 Class C networks).
Decimal: 255. 255. 192. 0
Binary: 11111111 11111111 11000000 00000000
If CIDR was not used, each of the 64 networks in this address range would need to be advertised separately. By using the CIDR address prefix, only one prefix needs to be advertised, making routing between networks easier and faster.
The term advertising in TCP/IP refers to routing tables that provide information about the hosts that can be reached from a particular IP address. CIDR enables fewer entries in the routing table for better performance.
Public and Private IP Addresses
A public IP address is one that faces the Internet and can be seen by any computers that connect to the Internet. For example, for google.com to have a properly functioning web server, the web server needs to have a public IP address. If it didn’t, no one would be able to connect to it. Private IP addresses are hidden from sight; usually they are behind a firewall. If your computer has an IP address on the 192.168.0 or 192.168.1 networks, it is a private IP address, and you most likely have a router that is protecting your IP from the Internet. Each IPv4 class has its own range of private IP addresses:
Class A—Uses the entire 10 network, from 10.0.0.0 to 10.255.255.255
Class B—Uses the range 172.16.0.0 through 172.31.255.255
Class C—Uses the range 192.168.0.0 through 192.168.255.255
Computers on a LAN normally are given private IPs, whereas servers on the Internet use public IPs.
Note
In some cases, you might need to determine the public IP address for a device on a private network. You can use a service such as IPLocation (www.iplocation.net) to find this information.
APIPA IP Addresses
Most IP networks use addresses provided automatically by dynamic host configuration protocol (DHCP). However, in the event that the DHCP server becomes unavailable and an alternate IP address has not been set up, devices on the network assign themselves APIPA/link-local addresses. These addresses are in the IPv4 address range of 169.254.0.1 to 169.254.255.254 (subnet mask of 255.255.0.0); the IPv6 version is called a link-local address with the FE80::/64 prefix. A device with an APIPA address cannot connect to the Internet.
To resolve the problem, users should check the device’s network connection and try using ipconfig/release and ipconfig/renew to obtain a new IP address from the DHCP server. If these actions don’t solve the problem, the DHCP server (often located in the router on a SOHO network) should be checked and restarted if necessary.
APIPA was originally developed by Microsoft, but it is now a standard (RFC 3927) that is also supported by OS X and Linux.
IPv6
IP version 6 enables a huge increase in the number of available IP addresses for computers, smartphones, and other mobile devices. IPv6 uses 128-bit source and destination IP addresses (compared to 32-bit for IPv4), enabling up to 340 undecillion addresses (3.4×1038). IPv6 also features built-in security, and provides better support for Quality of Service (QoS) routing, which is important to achieve high-quality streaming audio and video traffic. Windows, OS X, and Linux all support IPv6.
IPv6 Addressing
IPv6 addresses start out as 128-bit addresses that are then divided into eight 16-bit blocks. The blocks are converted into hexadecimal, and each block is separated from the following block by a colon. Leading zeros are typically suppressed, but each block must contain at least one digit.
Here is a typical IPv6 address:
21DA:D3:0:2F3B:2AA:FF:FE28:9C5A
A contiguous sequence of 16-bit blocks set to zero can be represented by :: (double colon). This technique is also known as zero compression. To determine the number of zero bits represented by the double colon, count the number of blocks in the compressed address, subtract the result from 8, and multiply the result by 16. An address can include only one zero-compressed block.
Here is an IPv6 address that does use the double colon:
FF02::2.
There are two blocks (FF02 and 2). So, how many zero bits are represented by the double colon? Subtract 2 from 8 (8–2=6, then multiply 6 by 16 (6 × 16=96). This address includes a block of 96 zero bits.
The loopback address on an IPv6 system is 0:0:0:0:0:0:0:1, which is abbreviated as ::1. Thus, if you want to test your network interface in Windows where IPv6 is enabled by default, you can type ping ::1.
IPv6 Address Types
IPv6 supports three types of addresses: unicast, multicast, and anycast. There are five types of unicast addresses:
Global unicast addresses are used in the same way as IPv4 public addresses. The first three bits are set to 001, followed by 45 bits used for the global routing prefix; these 48 bits are collectively known as the public topology. The subnet ID uses the next 16 bits, and the interface ID uses the remaining 64 bits.
Link-local addresses correspond to the Automatic Private IP address (APIPA) address scheme used by IPv4 (addresses that start with 169.254). The first 10 bits are set to FE80 hex, followed by 54 zero bits, and 64 bits for the Interface ID. Using zero compression, the prefix would thus be FE80::/64. As with APIPA, link local addresses are not forwarded beyond the link.
Site-local addresses correspond to IPv4 private address spaces (10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16).
Special addresses include unspecified addresses (0:0:0:0:0:0:0:0 or ::), which are equivalent to IPv4’s 0.0.0.0 and indicate the absence of an IP address; a loopback address (0:0:0:0:0:0:0:1 or ::1) is equivalent to the IPv4 loopback address of 127.0.0.1.
Compatibility addresses are used in situations in which IPv4 and IPv6 are both in use. In the following examples, w.x.y.z are replaced by the actual IPv4 address. An IPv4-compatible address (0:0:0:0:0:0:w.x.y.z or ::w.x.y.z) is used by nodes that support IPv4 and IPv6 communicating over IPv6. An IPv4-mapped address (0:0:0:0:0:FFFF:w.x.y.z or ::FFFF:w.x.y.z) represents an IPv4-only node to an IPv6 node. A 6to4 address is used when two nodes running both IPv4 and IPv6 connect over an IPv4 routing. The address combines the prefix 2002::/16 with the IPv4 public address of the node. ISATAP can also be used for the connection; it uses a locally administered ID of ::0:5EFE:w.x.y.z (w.x.y.z could be any unicast IPv4 address, either public or private); Teredo addresses are used for tunneling IPv6 over UDP through Network Address Translation (NAT); they use the prefix 3FFE:831F::/32.
Both IPv4 and IPv6 support multicasting, which enables one-to-many distribution of content such as Internet TV or other types of streaming media. IPv6 multicast addresses begin with FF.
Anycast addressing sends information to a group of potential receivers that are identified by the same destination address. This is also known as one-to-one-to-many association. Anycast addressing can be used for distributed services, such as DNS or other situations in which automatic failover is desirable. IPv6 uses anycast addresses as destination addresses that are assigned only to routers. Anycast addresses are assigned from the unicast address space.
Viewing IP Address Information
To see the IPv4 and IPv6 addresses assigned to a Windows device using both IPv4 and IPv6, use the command-line ipconfig utility. Here’s an example of the output from a system using a wireless Ethernet adapter:
Wireless LAN adapter Wireless Network Connection:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::5cf1:2f98:7351:b3a3%12
IPv4 Address. . . . . . . . . . . : 192.168.1.155
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.1.1
For more information, see http://technet.microsoft.com/en-us/library/dd392266(WS.10).aspx.
OS X provides this information through the TCP/IP tab of the Network utility (see Figure 11-9).
Many Linux distros include a GUI-based network utility similar to the one used in OS X, but with any Linux distro (as well as with OS X), you can open Terminal and use the command ifconfig –a to view this information. Figure 11-10 shows a portion of the output for a wireless connection.
Dynamic versus Static IP Addresses
There are two ways to configure a computer’s TCP/IP settings:
Dynamic (DHCP server-assigned) IP address
Table 11-5 compares the differences in these configurations.
Windows, OS X, and Linux default to using a dynamic IP address. As Table 11-5 makes clear, this is the preferable method for configuring a TCP/IP network. Use a manually assigned IP address if a Dynamic Host Configuration Protocol (DHCP) server (which provides IP addresses automatically) is not available on the network—or if you need to configure a firewall or router to provide different levels of access to some systems and you must specify those systems’ IP addresses.
Note
Routers, wireless gateways, and computers that host an Internet connection shared with Windows’s Internet Connection Sharing or a third-party sharing program all provide DHCP services to other computers on the network.
To configure TCP/IP in Windows, access the Internet Protocol Properties window; this window contains several dialogs used to make changes to TCP/IP. To open the General tab of the Internet Protocol Properties window, open Network Connections, right-click the network connection, select Properties, click Internet Protocol v4 (TCP/IPv4) or TCP/IPv6 in the list of protocols and features, and click Properties.
TCP/IP configuration in Linux is performed by editing the /etc/network interfaces file. If you use a GUI that features a Network configuration panel, you can use it to make changes for you.
To configure TCP/IP in OS X, go to System Preferences, open the Network panel, and select the appropriate tab (refer to Figure 11-9).
Client-Side DHCP Settings
Client-side DHCP settings are used to configure a workstation to receive its IP address from a DHCP server. Figure 11-11 shows the Windows 8.1 TCP/IPv4 properties General tab as it appears when a DHCP server is used.
Figure 11-11 The General tab is configured to obtain IP and DNS server information automatically when a DHCP server is used on the network.
Note
To determine the IP address, default gateway, and DNS servers used by a system using DHCP addressing, open a command prompt and enter the ipconfig /all command.
TCP/IP Alternate Configuration
The Alternate Configuration tab shown in Figure 11-12 is used to set up a different TCP/IPv4 configuration for use when a DHCP server is not available or when a different set of user-configured settings is needed, as when a laptop is being used at a secondary location. By default, automatic private IP addressing (APIPA) is used when no DHCP server is in use. As mentioned earlier in the chapter, APIPA assigns each system a unique IP address in the 169.254.x.x range. APIPA enables a network to perform LAN connections when the DHCP server is not available. However, systems with APIPA addresses cannot connect to the Internet. Linux and OS X refer to this type of connection as IPv4 link-local.
Figure 11-12 The Alternate Configuration tab is used to set up a different IP configuration for use on another network or when no DHCP server is available.
You can also use the Alternate Configuration tab to specify the IP address, subnet mask, default gateway, DNS servers, and WINS servers. This option is useful if this system is moved to another network that uses different IP addresses for these servers.
Note
In IPv6, all devices are assigned a link-local address using the prefix fe80::/64, even if a DHCP server is running or a manual IPv6 address has been assigned.
Client-Side IP and DNS Addresses
When a DHCP server is not used for a Windows device, the General tab is used to set up the IP address, subnet mask, default gateway, and DNS servers used by the network client. (The information shown in Figure 11-13 is fictitious.)
With OS X, use the TCP/IP tab (refer to Figure 11-9) to configure IPv4 or IPv6 address information. OS X uses the term router to refer to the default gateway. Use the DNS tab to configure DNS server information.
With Linux, you can use the network configuration tool provided in the GUI, or edit the network configuration scripts from Terminal using the distro’s text editor if no GUI-based network configuration program is available. There are two scripts that need to be edited:
ifcfg-connection name is used to identify IP addresses for IPv4 and IPv6 and the default gateway as well as other IP settings. It is located in the /etc/sysconfig/network-scripts/ folder. The loopback script is called ifcfg-lo. There is a separate ifcfg file for each connection (wired, wireless, and so on).
The file resolv.conf is used to identify DNS servers. It is located in the /etc/ folder.
For syntax, see the documentation for the distribution in use.
For the 220-901 exam be sure you understand the difference between static and dynamic IP addressing and where to go within a given operating system to set or change client-side DHCP, DNS, subnet mask, and default gateway settings.
Client-Side DNS Configuration
The Internet uses the domain name service (DNS) to map domain names, such as www.microsoft.com, to their corresponding IP address or addresses. A computer using the Internet must use at least one DNS server to provide this translation service. Use the client-side DNS Configuration tab to set up the computer’s host name, domain name, and DNS servers (refer to Figure 11-13) if the computer doesn’t use DHCP to obtain an IP address.
Note
Most ISPs and networks have at least two DNS name servers to provide backup in case one fails. Be sure to enter the IP addresses of all DNS servers available to your network. In Windows, these are referred to as preferred and alternate DNS servers.
Caution
Can’t access the site you’re looking for? Got the wrong site? You might have made one of these common mistakes:
Don’t assume that all domain names end in .com—Other popular domain name extensions include .net, .org, .gov, .us, .cc, and various national domains such as .uk (United Kingdom), .ca (Canada), and many others.
Don’t forget to use the entire domain name in the browser—Some browsers add the www. prefix used on most domain names, but others do not. For best results, spell out the complete domain name.
If you want a unique domain name for either a website or e-mail, the ISP that you use to provide your e-mail or web hosting service often provides a registration wizard you can use to access the domain name registration services provided by various companies such as Verisign.
A domain name has three major sections, from the end of the name to the start:
The top-level domain (.com, .org, .net, and so on).
The name of the site.
The server type; www indicates a web server, ftp indicates an FTP server, mail indicates a mail server, and search indicates a search server.
For example, Microsoft.com is located in the .com domain, typically used for commercial companies. Microsoft is the domain name. The Microsoft.com domain has the following servers:
www.microsoft.com hosts web content, such as product information.
support.microsoft.com hosts the Microsoft.com support website, where users can search for Knowledge Base (KB) and other support documents.
ftp.microsoft.com hosts the File Transfer Protocol server of Microsoft.com; this portion of the Microsoft.com domain can be accessed by either a web browser or an FTP client.
Many companies have only WWW servers, or only WWW and FTP servers.
Note
Some small websites use a folder under a domain hosted by an ISP: www.ispname.com/~smallsitename.
TCP/IP User-Configured Advanced Settings
In Windows, click the Advanced button shown in Figure 11-13 to bring up a multitabbed dialog for adding, editing, or removing gateways (IP Settings), DNS server addresses (DNS), and adjusting WINS resolution settings (WINS). These options can be used whether DHCP addressing is enabled or not. Figure 11-14 shows these tabs.
Gateway
A gateway is a computer or device (such as a router) that provides a connection between a LAN and a wide area network (WAN) or the Internet. OS X uses the term router to refer to the default gateway.
Computers that use a LAN connection to connect to the Internet need to enter the IP address of the default gateway on this tab if the computer doesn’t use DHCP to obtain an IP address.
If a computer on a LAN cannot reach the Internet, it is likely the default gateway is down or the default gateway address is misconfigured in the TCP/IP properties on the client-side.
TCP and UDP Ports, Protocols, and Purposes
For two computers to communicate, they must both use the same protocol. For an application to send or receive data, it must use a particular protocol designed for that application and open up a port on the network adapter to make a connection to another computer. For example, let’s say you want to visit www.google.com. You would open a browser and type http://www.bing.com. The protocol being used is HTTP, short for Hypertext Transfer Protocol, which makes the connection to the web server: google.com. The HTTP protocol would select an unused port on your computer (known as an outbound port) to send and receive data to and from google.com. On the other end, bing.com’s web server will have a specific port open at all times ready to accept sessions. In most cases the web server’s port is 80, which corresponds to the HTTP protocol. This is known as an inbound port.
Transmission Control Protocol (TCP) sessions are known as connection-oriented sessions. This means that every packet that is sent is checked for delivery. If the receiving computer doesn’t receive a packet, it cannot assemble the message and will ask the sending computer to transmit the packet again. No one packet is left behind.
User Datagram Protocol (UDP) sessions are known as connectionless sessions. UDP is used in streaming media sessions, Voice over IP (VoIP), for protocols that use a simple query and response such as DNS, and gaming. In these cases if a packet is dropped, it is not asked for again. Let’s say you were listening to some streaming music and you heard a break in the song or a blip of some kind. That indicates some missing packets, but you wouldn’t want those packets back because by the time you get them you would be listening to a totally different part of the music stream.
It’s expected to lose packets in UDP streams, but not when making TCP connections. Both TCP and UDP utilize ports to make connections. Remember, it’s the inbound ports that you are concerned with. For example, an FTP server that stores files for customers needs to have inbound port 21 open by default. Table 11-6 displays some common protocols and their default corresponding inbound ports. Most use the same TCP and UDP port numbers, but Table 11-6 lists exceptions.
Tip
Know these protocols and their corresponding port numbers for the exam.
In the following sections, you learn more about each of these protocols.
FTP
File Transfer Protocol (FTP) is a protocol used by both web browsers and specialized FTP programs to access dedicated file transfer servers for file downloads and uploads. When you access an FTP site, the site uses the prefix ftp://.
Windows and Linux contain a command-line FTP program; type FTP, press Enter, and then type help at the FTP prompt to see the commands you can use. See http://linux.about.com/od/commands/l/blcmdl1_ftp.htm.
For OS X, see http://osxdaily.com/2011/02/07/ftp-from-mac/ or use ftp from the command line.
FTP sites with downloads available to any user support anonymous FTP; if any credentials are required, it’s typically the user’s e-mail address as a password (the username is preset to anonymous). Some FTP sites require the user to log in with a specified username and password. FTP is not considered secure because FTP users can authenticate in clear-text sign-ins. FTP is often secured with SSL/TLS (FTPS) or use SSH File Transfer Protocol (SFTP) instead. FTP uses port 21.
Tip
Although you can use an operating system’s built-in FTP client for file uploads and downloads with both secured and unsecured FTP sites, you should consider using third-party FTP products such as FileZilla (http://filezilla-project.org/). These programs enable you to create a customized setup for each FTP site you visit and will store passwords, server types, and other necessary information. They also enable faster downloads than typical web browsers running in ftp:// mode.
SSH
Secure Shell (SSH) allows data to be exchanged between computers on a secured channel. This protocol offers a more secure replacement to FTP and Telnet. The Secure Shell server housing the data you want to access would have port 22 open (SSH uses port 22). Several other protocols use SSH as a way of making a secure connection. One of these is Secure FTP (SFTP) as previously mentioned. Regular FTP can be insecure. SFTP combats this by providing file access over a reliable data stream, generated and protected by SSH.
Telnet
Telnet enables a user to make a text-based connection to a remote computer or networking device and use it as if he were a regular user sitting in front of it, rather than simply downloading pages and files as he would with an http:// or ftp:// connection.
Windows and Linux contain a command-line Telnet program. To open a connection to a remote computer, open a command prompt (Windows) or terminal session (Linux) and type telnet and press the Enter key. This command opens the Telnet command prompt. For help with commands, type help and press the Enter key.
OS X includes a menu-driven Telnet program available from Terminal. See http://www.wikihow.com/Use-Telnet-on-OS-X.
The remote computer must be configured to accept a Telnet login. Typically, TCP port 23 on the remote computer must be open before a login can take place.
SMTP
The Simple Mail Transfer Protocol (SMTP) is used to send e-mail from a client system to an e-mail server, which also uses SMTP to relay the message to the receiving e-mail server. SMTP uses port 25.
Note
When configuring e-mail settings on a client, you need to know the server type(s) used (SMTP, POP3 or IMAP); the ports used (default values may be changed by some ISPs); the user name and password for the e-mail service; the security settings (for example, whether SSH is used). Check with the ISP or organization that provides Internet access for the correct values.
DNS
The domain name service (DNS) is the name for the network of servers on the Internet that translate domain names, such as www.informit.com, and individual host names into their matching IP addresses. If you manually configure an IP address, you typically provide the IP addresses of one or more DNS servers as part of the configuration process. DNS uses port 53.
HTTP/HTTPS
Hypertext Transfer Protocol (HTTP) is the protocol used by web browsers, such as Internet Explorer, Microsoft Edge, Firefox, and Chrome, to access websites and content. Normal (unsecured) sites use the prefix http:// when accessed in a web browser. Sites (HTTPS) that are secured with various encryption schemes are identified with the prefix https://. HTTP uses port 80 and HTTPS uses port 443.
Note
Most browsers connecting with a secured site will also display a closed padlock symbol onscreen.
POP3
The Post Office Protocol version 3 (POP3) is the more popular of two leading methods for receiving e-mail (IMAP is the other). In an e-mail system based on POP3, e-mail is downloaded from the mail server to folders on a local system. POP3 is not a suitable e-mail protocol for users who frequently switch between computers because e-mail might wind up on multiple computers. The POP3 version is the latest current standard. Users that utilize POP3 servers to retrieve e-mail typically use SMTP to send messages. POP3 uses port 110.
Tip
For users who must use POP3-based e-mail and use multiple computers, a remote access solution, such as Windows Remote Desktop Connection or a service such as GoToMyPC, is recommended. A remote access solution enables a user to remotely access the system that connects to the POP3 mail server so she can download and read e-mail messages, no matter where she is working.
IMAP
The Internet Message Access Protocol (IMAP) is an e-mail protocol that enables messages to remain on the e-mail server so they can be retrieved from any location. Compare it to POP3, which downloads messages to the mail client. IMAP also supports folders, so users can organize their messages as desired. IMAP4 is the current version of IMAP.
To configure an IMAP-based e-mail account, you must select IMAP as the e-mail server type and specify the name of the server, your username and password, and whether the server uses SSL. IMAP uses port 143.
SMB/CIFS
Server Message Block (SMB) provides access to shared items such as files and printers. They are actual packets that authenticate remote computers through what are known as interprocess communication mechanisms. SMB uses ports 137–139 for SMB traffic using NetBIOS over TCP (NBT), and 445 (SMB hosted on TCP).
Port 445 is also used by the Common Internet File System (CIFS). CIFS was widely used after its introduction as a standard method for sharing files across corporate intranets and the Internet. CIFS is an enhanced version of Microsoft SMB, which is an open, cross-platform protocol. CIFS has now been widely replaced by updated versions of SMB (SMB 2.0 and 3.0).
Note
If traffic on ports 137–139 is blocked, you must use the device’s IP address to access shared files or printers. When these ports are open, you can use the name of the device to access its shared files or printers.
AFP
Apple Filing Protocol (AFP) was previously known as AppleTalk Filing Protocol. AFP uses TCP/IP for transport, and is used by OS X 10.9 (Mavericks) and newer versions to connect to devices running older Mac OS and OS X versions, and for Apple’s Time Machine backup app.
Starting with OS X 10.9, OS X uses SMB2 to connect between OS X devices, Linux devices, or with Windows devices.
Remote Desktop Protocol
The RDP port, 3389, is used by Remote Desktop Services (RDS), which is the Windows Server-based companion of Remote Desktop Connection. To learn more about Remote Desktop Connection, see “Remote Desktop Connection,” p.791, Chapter 15.
SSL
Secure Socket Layers (SSL) is an encryption technology used by secured (https://) websites. To access a secured website, the web browser must support the same encryption level used by the secured website (normally 128-bit encryption) and the same version(s) of SSL used by the website (normally SSL version 2.0 or 3.0). Sites secured with SSL display a padlock in the browser’s URL and often a green address bar if secured by a certificate.
TLS
Transport Layer Security (TLS) is the successor to SSL. SSL3 was somewhat of a prototype to TLS and was not fully standardized. TLS was ratified by the IETF in 1999. However, many people and companies might still refer to it as SSL.
HTML
Hypertext Markup Language (HTML) is the language used by web pages. An HTML page is a specially formatted text page that uses tags (commands contained in angle brackets) to change text appearance, insert links to other pages, display pictures, incorporate scripting languages, and provide other features. Web browsers, such as Microsoft Internet Explorer, Microsoft Edge, Google Chrome, and Firefox, are used to view and interpret the contents of web pages, which have typical file extensions such as .htm, .html, .asp (Active Server pages generated by a database), and others.
You can see the HTML code used to create the web page in a browser by using the View Source or View Page Source menu option provided by your browser. Figure 11-15 compares what you see in a typical web page (main window) with the HTML tags used to set text features and the underlined hyperlink (inset window). The figure uses a different text size and shading to distinguish tags from text, and so do most commercial web-editing programs used to make web pages.
Figure 11-15 A section of an HTML document as seen by a typical browser uses the HTML tags shown in Notepad for paragraphs (<P>) titles (<H4>, </H4>), and hyperlinks (<A HREF>, </A>).
Tags such as <P> are used by themselves and other tags are used in pairs. For example, <A HREF...> is used to indicate the start of a hyperlink (which will display another page or site in your browser window), and </A> indicates the end of a hyperlink.
Note
The World Wide Web Consortium (http://www.w3c.org) sets the official standards for HTML tags and syntax.
DHCP
The Dynamic Host Configuration Protocol (DHCP) is used to automatically assign IP addresses to hosts. These hosts could be computers, printers, servers, routers, and so on. In most SOHO networks a router uses DHCP to assign IP addresses to the client computers. However, your ISP also uses DHCP to assign an IP address to you; usually your router gets this. The DHCP service makes life easier for the network administrator by automatically assigning IP addresses, subnet masks, gateway addresses, DNS servers, and so on. If you get your address from a DHCP server, you are getting your address assigned dynamically, and it could change periodically. However, some computers require a static address, one that is assigned by the network administrator manually. It is better in many situations for servers and printers to use static addresses, so you know exactly what the address is, and so it won’t change.
SNMP
Simple Network Management Protocol (SNMP) is used as the standard for managing and monitoring devices on your network. It manages routers, switches, and computers and is often incorporated in software known as a network management system or NMS. The NMS is the main software that controls everything SNMP-based; it is installed on a computer known as a manager. The devices to be monitored are known as managed devices. The NMS installs a small piece of software known as an agent that allows the NMS to monitor those managed devices.
LDAP
Lightweight Directory Access Protocol (LDAP) is used to access and maintain distributed directories of information such as the kind involved with Microsoft domains. Microsoft refers to this as directory services.
WiFi (Wi-Fi) Network and Encryption Standards
Wireless Ethernet, also known as IEEE 802.11, is the collective name for a group of wireless technologies compatible with wired Ethernet; these are referred to as wireless LAN (WLAN) standards. Wireless Ethernet is also known as Wi-Fi, after the Wireless Fidelity (Wi-Fi) Alliance (www.wi-fi.org), a trade group that promotes interoperability between different brands of Wireless Ethernet hardware.
Wi-Fi Standards
There are five different Wi-Fi standards:
802.11b has a maximum speed of 11Mbps and can fall back to 5.5Mbps or slower if necessary. It uses the 2.4GHz frequency band with 20MHz-wide channels.
802.11a has a maximum speed of 54Mbps and supports slower speeds from 6–48Mbps as needed and uses the 5GHz frequency band.
802.11g has a maximum speed of 54Mbps and supports slower speeds from 6–48Mbps as needed. Unlike 802.11a, 802.11g uses the 2.4GHz frequency band, so it is backward-compatible with 802.11b.
802.11n has a maximum speed of 150Mbps when using a single 20MHz channel, or up to 300Mbps when using channel bonding (40MHz channel). All 802.11n devices use the 2.4GHz frequency by default, but 802.11n can optionally support 5GHz frequencies as well. 802.11n supports MIMO (multiple in, multiple out) antennas to improve performance and range, although not all devices include multiple antennas.
802.11ac uses only the 5GHz band and supports up to 80MHz wide channels, compared to 20MHz with 802.11b/g and 40MHz with 802.11n using channel bonding. It supports Multi-user MIMO (MU-MIMO). The speed of 802.11ac is up to 433Mbps per stream when 80MHz wide channels are used.
Table 11-7 compares different types of Wireless Ethernet to each other.
Wi-Fi–certified hardware is 802.11-family Wireless Ethernet hardware that has passed tests established by the Wi-Fi Alliance. Most, but not all, 802.11-family Wireless Ethernet hardware is Wi-Fi–certified.
Understanding MIMO
The number of antennas supported by the router and the adapters (either built-in or add-on devices) is one of the reasons for different performance levels in a given 802.11n or 802.11ac device:
1x1—one transmit, one receive antenna
2x2—two transmit, two receive antennas
2x3—two transmit, three receive antennas
3x2—three transmit, two receive antennas
3x3—three transmit, three receive antennas
The number of transmit antennas generally corresponds to the number of spatial streams (data streams) the device can support. In the case of a router that supports both 2.4GHz and 5GHz signals, the specifications include this information for each band.
When a device has a different number of receiving and sending antennas, the device might be identified by the number of spatial (data) streams it can send and receive. For example, a device with a 2x3 antenna configuration can also be identified as having a 2x3:2 configuration (two send antennas, three receive antennas, and two spatial [data] streams send/receive support). Some smartphones and tablets simply use the term MIMO (multiple input, multiple output) if they support two or more 802.11n or 802.11ac streams.
Wi-Fi Encryption Types
Although many public Wi-Fi hot spots are not encrypted, encryption is a necessity for both SOHO and larger business wireless networks to preserve privacy and to prevent criminals from borrowing your network. However, there are several types of encryption.
WEP (Wired Equivalent Privacy)
WEP is the oldest and weakest Wi-Fi encryption standard. All network devices must use the same WEP key and encryption strength if WEP is enabled.
Use the highest setting supported by both WEP and adapters for best security. Small-office or home-office hardware might use 64-bit encryption with a 40-bit key (10 hexadecimal characters or 5 ASCII characters); business-market hardware often uses 128-bit encryption with a 104-bit key (26 hexadecimal characters or 13 ASCII characters). WEP cannot use punctuation marks in its encryption keys.
WEP can be configured using a pre-shared key (PSK) or Open System authentication. PSK is easier to break than Open System, but either form is easy to break and should not be used unless some network devices don’t support superior WPA or WPA2 encryption. 802.11n and 802.11ac do not support WEP.
WPA (Wi-Fi Protected Access)
WPA uses a variable-length encryption key (up to 63 ASCII characters including punctuation marks) and temporal key integrity protocol (TKIP) 128-bit encryption, making it much more secure than WEP.
WPA can use PSK or a RADIUS authentication server to generate unique keys (used in enterprise and government Wi-Fi networks).
WPA has been largely replaced by WPA2, but some routers can be configured to support both WPA and WPA2 clients on the same network.
WPA2 (Wi-Fi Protected Access 2)
Unlike most sequels, this sequel is better (in the sense of being more secure) than the original. WPA2 replaces TKIP with advanced encryption standard (AES), a 128–256-bit encryption protocol used in several technologies such as hard drive encryption as well as networking. It can be used exclusively or in conjunction with TKIP and is the recommended option. Some router configurations use the term WPA-AES to refer to WPA2. If you use a mixture of WPA and WPA2 devices and can’t update the firmware on the older devices to support AES, use the WPAs-TKIP-AES setting on your router.
WPS (Wi-Fi Protected Setup)
WPS is simply an easier way to configure a wireless network than entering the router’s IP address on each device connecting to it. Routers that support WPS typically have the default WPS key on the bottom of the device. To use WPS, use the setup software provided with the router on each computer and follow the directions on devices such as printers or multifunction. Note that WPS should not be used unless all devices on a wireless network support it.
There are two ways to use WPS: the default PIN method (in which the PIN on the router is used to set up clients) and a pushbutton method, in which a physical or software button is pushed on the router and clients to set up the network. In December 2011, researchers announced that the PIN and the pre-shared key could be compromised by a brute-force attack. Since that time, users have been encouraged to use the pushbutton method or to forgo using WPS for configuration.
Table 11-8 compares WEP, WPA, and WPA2 to each other.
Configure SOHO Wired or Wireless Router
A small-office home-office (SOHO) wired or wireless router can provide a secure way for users to access the Internet and local network resources or become a magnet for attack. The difference is in how it is configured. In the following sections, we look at how to configure SOHO routers to meet typical network requirements.
Channels
When installing a 2.4GHz wireless network, avoiding overlapping channels and selecting a channel with little or no traffic can be challenging. Only channels 1, 6, and 11 do not overlap with other channels. Use one of these channels.
Some routers feature an Auto setting that will use the least-active channel, but if you prefer (or must) select a channel manually, use a Wi-Fi diagnostic utility (discussed later in this chapter) to find the least-used channel.
To change the channel used by your wireless network:
Step 1. Log in to your router.
Step 2. Navigate to the Wireless Configuration dialog.
Step 3. Select a different channel (when using 2.4GHz networking, channels 1, 6, and 11 have less interference than others).
Step 4. Save your changes and exit the router configuration dialog.
Figure 11-16 illustrates a typical wireless channel configuration dialog on a dual-frequency (2.4 and 5.0GHz) Wireless-N router from Western Digital.
NAT
Network address translation (NAT) is the process of modifying IP addresses as information crosses a router. Generally, this functionality is built into a router. It hides an entire IP address space on the LAN; for example, 192.168.0.1 through 192.168.0.255. Whenever an IP address on the LAN wants to communicate with the Internet, the IP is converted to the public IP of the router; for example, 68.54.127.95. This way, it appears that the router is the only device making the connection to remote computers on the Internet, providing safety for the computers on the LAN. It also allows a single IP to do the work for many IP addresses in the LAN.
SOHO routers perform NAT automatically when connected to an IPv4 network. NAT is not necessary on an IPv6 network because IPv6 is much more secure and has no shortage of IP addresses.
Port Forwarding, Port Triggering, and DNAT
Port forwarding is used to forward external visitors through the router to a specific computer. Instead of opening up the entire LAN, port forwarding directs particular traffic where you want it to go. A basic example would be if you were to set up an FTP server internally on your LAN. The FTP server might have the IP address 192.168.0.250 and have port 21 open ready to accept file transactions, or you could use a different inbound port if you want. Clients on the Internet that want to connect to your FTP server would have to know the IP address of your router, so for example the clients would connect with an FTP client using the IP 68.54.127.95 and port 21. Once you create the appropriate port-forwarding rule, the router would then see these packets and forward them to 192.168.0.250:21, or whatever port you choose. Now, many ISPs block this type of activity, but it becomes a common and important method in larger networks.
Figure 11-17 illustrates port forwarding for an incoming VPN that uses PPTP. PPTP uses two non-contiguous ports and thus needs two rules, one for each port.
Port triggering, which is available on some routers, opens an outgoing port or range of ports on demand by a particular service, such as internet relay chat (IRC). Port triggering can be used without tying it to a specific IP address.
Another name for port forwarding is destination network address translation (DNAT) DNAT is sometimes also used to refer to DMZ.
DMZ
A demilitarized zone (DMZ) allows outside traffic through to a particular IP address on your LAN. In a SOHO router, any device assigned to the DMZ receives traffic that is not specified for a particular device. Using a DMZ host makes sense for gaming or other types of traffic where you cannot specify in advance the ports needed. However, it’s important that the DMZ host has its own firewall, because DMZ hosts are not protected by the router firewall.
Figure 11-18 illustrates a typical DMZ configuration. After DMZ is enabled, the IP address for the device you are using as a DMZ host must be specified.
Tip
Use static IP addresses for any devices that use port forwarding or DMZ to assure that the correct device is being specified. Dynamic IP (server-assigned DHCP) addresses can change according to the number of devices on the network and whether some devices leave the network and then return to it.
DHCP
By default, SOHO routers have the DHCP service turned on, enabling them to provide IP addresses to any wired or wireless device that connects. Most routers enable you to specify the range and number of IP addresses available via DHCP. If a router does not have sufficient IP addresses for the devices that need to connect to it, devices arriving after the pool of addresses is used up will not receive an IP address and will switch to APIPA, the non-routable IP address range (169.254.x.x). Figure 11-19 illustrates a router with DHCP enabled and a range of IP addresses the DHCP server can assign.
Tip
When you need to use static IP addresses, make sure you don’t assign all possible IP addresses to the DHCP server, and use addresses beyond the DHCP range for those devices. For example, in the network illustrated in Figure 11-19, IP addresses below 100 and above 149 in the 192.168.1.x network could be used for devices needing static IP addresses.
Basic QoS
Quality of service (QoS) is an important feature to enable on any network that provides streaming media, gaming, or VoIP services. QoS prioritizes real-time and streaming traffic. Depending on the router, QoS can simply be turned on and off (Basic QoS) or it can be tweaked by specifying services to prioritize, whether to optimize for gaming, and uplink/downlink speeds to use.
QoS can be configured by your ISP or by your router. If your ISP is already performing QoS optimization, any changes you make on your router will not improve your traffic.
UPnP
Universal plug and play (UPnP) is a router feature that enables devices on your network to add themselves to your network without the need to reconfigure your router. UPnP is widely used for media streaming across a network.
However, UPnP can be vulnerable to attacks. If you don’t use media streaming or other services that use UPnP, you can disable it.
Firmware
Routers are specialized computing devices that are controlled by firmware. When you log into a router to view or change its configuration, the options you can choose are limited by its firmware. Buggy firmware can cause network problems or make your network more vulnerable to attack.
Use a router’s configuration program to determine the firmware date and version it uses. If the router is using an older version of firmware, check the vendor’s website for an update. Before downloading the update, read the technical notes to see what issues the firmware affects and if any other problems are caused by the update. Download the update and follow the vendor’s instructions for installing the firmware.
If you want more features than the vendor-provided firmware includes, check for third-party firmware. DD-WRT is the most popular replacement firmware for routers, and some vendors now use it in their high-end routers.
To determine if a router can use DD-WRT firmware, visit the router database at the DD-WRT website (www.dd-wrt.com) and look up the router. You need to know the brand, model number, and revision. Figure 11-20 illustrates a portion of the System Information dialog from a Netgear router running DD-WRT firmware.
Internet Connection Types
One of the best reasons to create a network of any size is to provide access to the Internet. The many types of connectivity technologies that can be used for Internet access are discussed in the following sections.
Note
As you review the following sections, try to determine which type of Internet connections you use at home and at your workplace. If you are shopping for Internet service, the Broadband Now website (www.broadbandnow.com) is a useful way to find all types of broadband Internet access available in a specified zip code.
Cable
Cable Internet service is provided by a cable TV company. Virtually all cable Internet service today is built upon the fiber-optic and coaxial network used for digital cable and music services provided by most cable TV vendors. In most cases today, separate coaxial cables are used for TV and for Internet service into home or office.
Cable Internet can reach download speeds anywhere from 3Mbps up to 300Mbps or faster. Upload speeds are typically about 10–20 percent of upload speeds, but vary by vendor.
Note
You can have cable Internet service without having cable TV.
Most cable modems connect to a computer or a router via an RJ-45 cable, but some use USB. When a cable provider also provides telephone service, a special modem is used that also includes a backup battery. A typical model is shown in Figure 11-21.
A cable Internet connection can be configured through the standard Network properties sheet in the operating system.
DSL
DSL (digital subscriber line) was originally designed to work on the same telephone line used by your telephone and fax machine if the telephone line can carry a digital signal. For home use, DSL is designed strictly for Internet access. But for business use, DSL can be used for additional services and can be used in site-to-site scenarios between organizations.
While telephone line–based DSL is still available, it is much slower than cable Internet. Newer types of DSL use the same signaling methods, but use fiber to provide speed comparable to high-performance cable.
There are two major types of DSL that use telephone lines: ADSL (Asynchronous DSL) and SDSL (Synchronous DSL). Two newer types of DSL, VDSL (very high bit-rate digital subscriber line) and VDSL2, use fiber for at least part of the signal path.
Their features are compared in Table 11-9.
Note
Downstream refers to download speed; upstream refers to upload speed. SDSL gets its name from providing the same speed in both directions; ADSL is always faster downstream than upstream.
Both VDSL and VDSL2 use fiber for most of the distance from the telephone company’s central office (where all DSL services connect to the Internet).
A device known as a DSL modem is used to connect your computer to DSL service. DSL modems connect to your PC through the RJ-45 (Ethernet) port or the USB port. The rear of a typical DSL modem that uses an Ethernet (RJ-45) connection is shown in Figure 11-22.
Figure 11-22 The rear of a typical ADSL modem with a power port (top left), RJ-45 data port to the PC (top center), and an RJ-11 telephone line port (top right). The RJ-45 cable is shown at bottom left, and the RJ-11 cable is shown at bottom right.
Many companies offering ADSL, VDSL, or VDSL2 services now provide a wireless router with DSL support and an integrated Gigabit Ethernet switch. Some of these devices also support HPNA, which uses coaxial wiring in the home as a network, or connections to a cable modem.
As Figure 11-23 indicates, DSL uses the same telephone lines as ordinary telephone equipment. However, your telephone can interfere with the DSL connection. To prevent this, in some cases a separate DSL line is run from the outside service box to the computer with the DSL modem. However, if your DSL provider supports the self-installation option, small devices called microfilters are installed between telephones, answering machines, fax machines, and other devices on the same circuit with the DSL modem. Microfilters can be built in to special wall plates but are more often external devices that plug into existing phone jacks, as shown in Figure 11-23.
Figure 11-23 A typical self-installed DSL setup. The DSL vendor supplies the DSL modem (center) and microfilters that attach between telephones and other devices and the wall outlet (right).
Some DSL connections are configured as an always-on connection similar to a network connection to the Internet. However, many vendors now configure the DSL connection as a PPPoE (point-to-point protocol over Ethernet) connection instead. A PPPoE connection requires the user to make a connection with a username and password. PPPoE connections are supported in Windows, OS X, and Linux.
Dial-up
Until the late ’90s, dial-up networking (DUN) was the most common way for home and small businesses to connect to the Internet. Today, dial-up connections are used when no other Internet connection is available. Dial-up connections are often referred to as analog connections because the device used to make the connection is an analog modem, which connects to the Internet through an ordinary telephone line.
Modem Technologies and Types
A modem sending data modulates digital computer data into analog data suitable for transmission over telephone lines to the receiving modem, which demodulates the analog data back into computer form.
Note
Properly used, the term modem (modulator-demodulator) refers only to a device that connects to the telephone line and performs digital-to-analog or analog-to-digital conversions. However, other types of Internet connections such as satellite, wireless, DSL, fiber and cable Internet also use the term modem, although they work with purely digital data. When used by itself in this book, however, modem refers only to dial-up (telephone) modems.
Modems come in many form factors, the most common of which include:
Add-on card—Add-on card modems for desktop computers fit into a PCI expansion slot. See Figure 5-12 on page 141, Chapter 5, for a typical example.
External—External modems plug into a serial or USB port.
Mini-PCI card—Some older-model computers that appear to have built-in modems actually use modems that use the mini-PCI form factor and can be removed and replaced with another unit.
Although some high-end add-on card modems have a hardware universal asynchronous receiver transmitter (UART) or UART-equivalent chip, most recent models use a programmable digital signal processor (DSP) instead. Modems with a DSP perform similarly to UART-based modems but can easily be reprogrammed with firmware and driver updates as needed. Low-cost add-on card modems often use host signal processing (HSP) instead of a UART or DSP. HSP modems are sometimes referred to as Winmodems or soft modems because Windows and the computer’s processor perform the modulation, slowing down performance. HSP modems might not work with some older versions of Windows or non-Windows operating systems such as Linux or OS X.
External modems must be connected to a serial or USB port. Serial port versions require an external power source (USB modems are usually powered by the USB port or hub), but the portability and front-panel status lights of either type of external modem make them better for business use.
There have been various standards for analog modems used to make dial-up connections. Before the advent of so-called “56K” standards, the fastest dial-up connection possible was 33.6Kbps. Virtually all modems in more recent systems or available for purchase support either the ITU v.90 or v.92 standards.
Note
Although v.90 and v.92 modems are all designed to perform downloading at up to 56Kbps, FCC (Federal Communications Commission) regulations limit actual download speed to 53Kbps. Speeds greater than 33.6Kbps apply only to downloads from Internet service providers (ISPs) and their special modems. If you make a direct connection between two PCs, the fastest speed you can have in either direction is just 33.6Kbps (if both modems can run at least that fast).
Note
You can drive yourself crazy trying to make a connection with your modem if you plug the RJ-11 telephone cord into the wrong jack. There are actually three ways to make this mistake:
Plugging in the RJ-11 cord to the phone jack instead of the line or telco jack on the modem
Plugging in the RJ-11 cord to the slightly larger RJ-45 jack used for 10/100/1000 Ethernet networking
Plugging in the RJ-11 cord to a HomePNA network card (which also has two RJ-11 jacks) instead of the modem
Requirements for a Dial-Up Internet Connection
All dial-up ISPs must provide the following information to enable you to connect to the Internet:
TCP/IP configuration information
Dial-up access telephone numbers
Modem types supported (33.6Kbps, 56Kbps, v.90, v.92)
The username and initial password (which should be changed immediately after first login)
Even if the client software provided by the ISP configures the connection for you, you should record the following information in case it is needed to manually configure or reconfigure the connection:
The dial-up access telephone number—Dialing prefix, area code, and phone number are needed.
The username and password—Windows often saves this during the setup of a DUN connection, but it should be recorded in case the system must be reconfigured or replaced.
The TCP/IP configuration—This is set individually for each dial-up connection through its properties sheet.
To determine this information, right-click the icon for the connection and select Properties.
Creating a Dial-Up Connection
Windows creates dial-up networking (DUN) connections within the Network and Sharing Center window. To create a dial-up connection:
Step 1. Click Connect to a network.
Step 2. Choose Set up a dial-up connection.
Step 3. If your modem is not connected, click Set up a connection anyway to continue. Your settings will be saved.
Step 4. Enter the phone number, the user name (usually your e-mail address) and password assigned by the ISP, and name the connection. If you need to set dialing rules (such as numbers to reach an outside line), click the Dialing Rules link.
Step 5. Click Create or Connect (see Figure 11-24).
If the dial-up connection is the only network connection, it appears when you open your browser. If you have other connections, you can select the connection to use from the Internet Options dialog’s Connections tab.
To create a dial-up connection with OS X:
Step 1. Open the Network dialog.
Step 2. Select the modem from the list of network devices.
Step 3. Enter the phone number, the user name (usually your e-mail address) and password assigned by the ISP.
Step 4. To see the modem status in the menu bar, select the checkbox.
Step 5. Click Apply.
In Linux, you can create a dial-up connection using the Network configuration features in the GUI or by using the wvdial and wvdialconf programs and editing the wvdial.conf configuration file to specify the phone number, username, and password assigned by your ISP. For details, see http://www.tldp.org/HOWTO/PPP-HOWTO/x314.html.
Fiber
Instead of using a copper connection to the home or business the way dial-up, ADSL/SDSL, or cable Internet do, many companies offer fiber (fiber-optic cable) connections to the home (FTTH, also known as fiber to the premises or FTTP) at their highest service levels. Fiber network download speeds can reach up to 2Gbps, and some vendors provide the same upload speed. DSL vendors such as Verizon, AT&T, and CenturyLink offer fiber connections in some service areas, as does Google Fiber. Contact your ISP to determine if fiber connections are available or coming to your area.
The conversion between the fiber connection entering the home and the Ethernet or coaxial WAN connection used to connect a router or gateway is performed by an optical network terminal (ONT), which is supplied by the fiber provider and installed in the home.
Fiber users rent the router or gateway, which resembles the router or gateway included with cable or DSL Internet service, from the fiber provider. The fiber router or gateway connects to the ONT. Some vendors offer a network box that incorporates a wireless router as an alternative to a separate ONT and router or gateway.
Note
To learn more about FTTH/FTTP service in the USA, see Google Fiber (https://fiber.google.com/); Verizon Fios (http://www.verizon.com/home/fios/); AT&T U-verse with Gigapower (https://www.att.com/shop/u-verse/gigapower.html); or CenturyLink Fiber (https://www.centurylink.com/fiber/). Additional regional provider information is available at https://en.wikipedia.org/wiki/Fiber_to_the_premises_in_the_United_States.
Satellite
Satellite Internet providers, such as HughesNet (previously known as DirecWAY, and before that as DirecPC), StarBand, and WildBlue use dish antennas similar to satellite TV antennas to receive and transmit signals between geosynchronous satellites and computers. Separate antennas are needed for satellite Internet and TV services.
Note
Geosynchronous satellites orbit the Earth’s equator at a distance of more than 22,000 miles (approximately 35,000 kilometers). Because of their orbits and altitudes, they remain in the same location in the sky at all times. In the Northern Hemisphere, you need an unobstructed view of the southern sky to make a connection. In the Southern Hemisphere, you need an unobstructed view of the northern sky to make a connection.
Satellite Internet services use external devices often called satellite modems to connect the computer to the satellite dish. They connect to the USB or Ethernet (RJ-45) port in a fashion similar to that used by DSL or cable modems.
The FCC requires professional installation for satellite Internet service because an incorrectly aligned satellite dish with uplink capabilities could cause a service outage on the satellite it’s aimed at. Setup software supplied by the satellite vendor is used to complete the process.
Note
Satellite connections can also be made between buildings to allow for the high-speed exchange of data. In this scenario, a satellite dish would need to be installed on each building, and they would need to be in direct line of sight of each other. Internet access can also be offered in this manner.
ISDN
ISDN (Integrated Services Digital Network) was originally developed to provide an all-digital method for connecting multiple telephone and telephony-type devices, such as fax machines, to a single telephone line and to provide a faster connection for teleconferencing for remote computer users. A home/small office-based connection can also provide an all-digital Internet connection at speeds up to 128Kbps. Line quality is a critical factor in determining whether any particular location can use ISDN service. If an all-digital connection cannot be established between the customer’s location and the telephone company’s central switch, ISDN service is not available or a new telephone line must be run (at extra cost to you!).
Note
The telephone network was originally designed to support analog signaling only, which is why an analog (dial-up) modem that sends data to other computers converts digital signals to analog for transmission through the telephone network. The receiving analog modem converts analog data back to digital data.
ISDN Hardware
To make an ISDN connection, your PC (and any other devices that share the ISDN connection) needs a device called an ISDN terminal adapter (TA). A TA resembles a conventional analog modem. Internal models plug into the same PCIe or PCI slot used by analog modems, and external models use USB or serial ports.
Setting Up an ISDN Connection
ISDN connections (where available) are provided through the local telephone company. There are two types of ISDN connections:
Primary Rate Interface (PRI)—A PRI connection provides 1.536Mbps of bandwidth, whereas a BRI interface provides 64Kbps (single-channel) or 128Kbps (dual-channel) of bandwidth.
Basic Rate Interface (BRI)—BRI is sold to small businesses and home offices; PRI is sold to large organizations.
Both types of connections enable you to use the Internet and talk or fax data through the phone line at the same time.
A direct individual ISDN connection is configured through the network features of the operating system with the same types of settings used for an analog modem connection. Configuring a network-based ISDN connection is done through the network adapter’s TCP/IP properties window.
Note
Most telephone companies have largely phased out ISDN in favor of DSL, which is much faster and less expensive for Internet connections.
Line of Sight Wireless
Line of sight wireless, sometimes referred to as terrestrial wireless, uses small antennas to connect users to Internet service transmitted from microwave towers. As the name states, a clear line of sight must be available from the transmission tower to the customer site. In some cases, this means that the customer antenna must be placed on the roof or on its own stand, or trees must be trimmed to provide adequate signal quality.
To bring the network signal into the premises, coaxial cable connects from the antenna to a line of sight wireless modem (similar to a cable modem). Connect the modem to a router to provide multiple devices with Internet access.
Typical download speeds range from 256Kbps up to 10Mbps. To find information about a wireless Internet Service Provider (WISP) in your area, visit wispdirectory.com.
Network Types
A network is a group of computers, peripherals, and software that are connected to each other and can be used together. Special software and hardware are required to make networks work.
LAN
A LAN (local area network) is a group of computers and other devices usually located in a small area: a house, a small office, or a single building. The computers all connect to one or more switches, and a router allows the computers access to the Internet.
WAN
A WAN (wide area network) is a group of one or more LANs over a large geographic area. Let’s say a company had two LANs, one in New York and one in Los Angeles. Connecting the two would result in a WAN. However, to do this would require the help of a telecommunications company. This company would create the high-speed connection required for the two LANs to communicate quickly. Each LAN would require a router to connect to each other.
MAN
A smaller version of a WAN is known as a MAN (metropolitan area network), also known as a municipal area network. This is when a company has two offices in the same city and wants to make a high-speed connection between them. It’s different from a WAN in that it is not a large geographic area, but it is similar to a WAN in that a telecommunications company is needed for the high-speed link.
PAN
A PAN (personal area network) is a smaller computer network used for communication by smartphones, tablets, and other small personal computing devices, typically using Bluetooth.
Network Architecture Devices
To create, update, repair, or manage a network effectively, you must understand the hardware building blocks used in networking. The following sections cover these components, their functions, and their features.
Hub
A hub is the simplest device used on an Ethernet network for connecting devices to each other. Hubs feature multiple RJ-45 ports, a power supply and signal lights to indicate network activity. Stackable hubs can be connected together to provide more ports.
Hubs have been almost completely replaced by switches because hubs split the bandwidth of the connection among all the computers connected to it. For example, a five-port 10/100 Ethernet hub divides the 100Mbps speed of Fast Ethernet among the five ports, providing only 20Mbps of bandwidth to each port for Fast Ethernet and 10/100 adapters. A hub also broadcasts data to all computers connected to it.
Switch
A switch is similar to the hub in appearance, but when it comes to sending data it works differently. Each port on a switch works independently, allowing more than one concurrent session. The switch makes a direct connection between the sending and receiving device by identifying the MAC address of each device. In today’s networks, the switch is king and is common in 100Mbps, 1000Mbps, and 10Gbps networks. Switches, like hubs, are stackable.
A switch resembles a hub but creates a dedicated full-speed connection between the two computers that are communicating with each other. A five-port 10/100/1000 switch, for example, provides the full 100Mbps bandwidth to each port connected to a Fast Ethernet or 10/100 card. If the network adapters are configured to run in full-duplex mode (send and receive data simultaneously) and the switch supports full-duplex (most modern switches do), the Fast Ethernet bandwidth on the network is doubled to 200Mbps and Gigabit Ethernet (1000Mbps) bandwidth is doubled to 2Gbps. Switches can be daisy-chained in a manner similar to stackable hubs, and there is no limit to the number of switches possible in a network.
Low-cost switches used in SOHO networks (see Figure 11-25) are unmanaged. Managed switches, common in corporate and enterprise networks, also support simple network management protocol (SNMP) for diagnostics and performance measurement, support for Virtual LANs (VLANs) to enable multiple workgroups to use the same physical switch but keep their traffic separate, and redundancy.
Router
The router connects one network to another. For example, a router connected to a cable or DSL modem enables multiple devices on a LAN to share a single broadband connection.
Most routers sold for SOHO configurations are Wi-Fi (802.11-family) wireless routers with integrated Fast or Gigabit Ethernet switches. Both wired and wireless devices can be on the same network and share folders and printers as well as Internet access.
Figure 11-26 shows the rear of a typical 802.11ac router for cable Internet from ASUS.
Figure 11-26 Many wireless routers can now be used as hosts for USB drives for shared network storage.
A router used for DSL is similar in appearance, but features a DSL port. The switches built into routers are also stackable. If a router needs more ports, add a switch.
Wireless Access Point
While hubs and switches deal with wired networks, the wireless access point (WAP) deals with wireless connections. It is also based on Ethernet, but now we are talking about the IEEE 802.11 group of standards, which define wireless LANs (WLANs). Wireless access points act as a central connecting point for computers equipped with wireless network adapters; like switches, the WAP identifies each computer by its MAC address.
To turn a wireless router into a WAP (which would then need to connect to a separate router), check the configuration options available for the router.
Bridge
The bridge is a device that can either connect two LANs together or separate them into two sections. There are wired and wireless bridges that are more commonly used today to increase the size of networks.
Modem
Now, let’s move outside the LAN and talk about Internet and wide area network connectivity. The term modem is a conjunction of the words modulate and demodulate. Originally, the term modem was used only for analog (dial-up modems). It is a device that allows a computer (or in rare cases multiple computers) access to the Internet by changing the digital signals of the computer to analog signals used by a typical land-based phone line. These are slow devices and are usually used only if no other Internet option is available. However, they might be used in server rooms as a point of remote administration as well.
Today, any device that connects to the Internet is sometimes referred to as a modem.
Firewall
A firewall is any hardware appliance or software application that protects a computer from unwanted intrusion. In the networking world we are more concerned with hardware-based devices that protect an entire group of computers such as a LAN. When it comes to small offices and home offices, firewall functionality is usually built into the router. In larger organizations it is a separate device. The firewall stops unwanted connections from the outside and can block basic networking attacks.
Patch Panel
A patch panel is a box designed as a junction point for coaxial, TP, or fiber cable used in networks. Patch panels are typically built into wiring closets or added to equipment racks in a 1U or taller form factor. Patch panels can also be incorporated into homes or offices that have network or telephone wiring in the walls.
For a patch panel for TP cable, the patch panel must match the fastest cable grade in your network (CAT5e, CAT6, and so on). After removing any connector on the cable, each wire in the TP cable must be untwisted before being punched into the appropriate connection on the back of the panel. Use the same T568B or T568A color-coding that matches the rest of your network.
The front of the patch panel uses RJ-45 connectors for short standard network cables.
Repeaters/Extenders
Wireless network signals can be blocked by masonry, steel, or concrete walls and weaken over distance. By using a signal repeater or extender, areas of weak or no signals can also take advantage of a wireless network.
A wireless repeater (see Figure 11-27) resembles a wireless router and might sometimes include a switch, but instead of connecting to a cable or DSL modem, it connects wirelessly to your wireless router.
Figure 11-27 A wireless repeater. Adjust the antennas to improve connections to the wireless router elsewhere in the building.
A powerline extender kit can be used to extend wired or wireless Internet connections. Powerline adapters are sold in pairs: one unit plugs into an AC wall socket near the router and is connected to the router via a switch. The other unit plugs into an AC wall socket in the room or area that needs network/Internet access. The AC wiring in the home or office (as long as it’s on the same circuit) carries network signals between units. With a wired extender, plug a computer or switch into the Ethernet port. With a wireless extender, log into the network via the wireless extender’s SSID.
Figure 11-28 illustrates a typical wired powerline extender.
Power Over Ethernet
Power over Ethernet (PoE) uses CAT5 or better grades of TP cable to carry up to 25.5 watts of power on the unused TP pairs (pins 4-5, 7-8) in 10BASE-T or 100BASE-T Ethernet (PoE Mode B) or by using all four wire pairs (PoE Mode A), enabling it to be used with Gigabit Ethernet. PoE enables wireless access points, IP security cameras, VoIP phones, routers, and other Ethernet devices to be usable away from traditional power sources.
A PoE endspan device is a switch that supports PoE. A PoE midspan, also known as a power over Ethernet injector, is installed between a standard Ethernet switch and a PoE device to provide power only.
Using Networking Tools
If you plan on building a physical network, you need to stock up on some key networking tools. These tools aid you when running, terminating, and testing cable. For this short section, let’s imagine a scenario where you are the network installer and are required to install a wired network for 12 computers.
To start, you should check with your local municipality for any rules and regulations for running networking cable. Some municipalities require a person to have an electrician’s license. But most only require an exemption of some sort that anyone can apply for at the town or county seat. Due to the low-voltage nature of network wiring (for most applications), some municipalities have no rules regarding this. But in urban areas you need to apply for a permit and have at least one inspection done when you are finished with the installation.
Permits and regulations aside, let’s say that in this scenario you have been cleared to install 12 wired connections to computers (known as drops) and have diagrammed where the cables will be run and where they will terminate. All cables will come out of a wiring closet where you will terminate them to a small patch panel. On the other end, they will terminate at in-wall RJ-45 jacks near each of the computers. Let’s discuss each of the tools that you will use to complete this job.
Cutting Tool
The first tool you should have is a good, sharp cutting tool. You need to make a clean cut on the end of the network cable; scissors will not do. Either cut pliers or other cable cutting tools will be necessary. Klein Tools (www.kleintools.com) is an excellent manufacturer of these types of tools.
Cable Stripper
The second tool is a cable stripper. This tool is used to strip a portion of the plastic jacket off of the cable exposing the individual wires. At this point you can separate the wires and get ready to terminate them. Figure 11-29 illustrates a typical cable stripper.
Crimper
A crimper attaches a connector to the end of raw TP or coaxial cable. There are two types of crimpers you might need. If you are working with TP, you need an RJ-45 crimping tool (some also work with RJ-11 telephone cable). After untwisting the wire pairs and aligning them according to the appropriate standard (typically T568B), insert them into an RJ-45 connector and push the cable and connector assembly into the crimper. Line up the crimper jaw with the recessed area of the connector, and squeeze (see Figure 11-30).
If you are working with coaxial using F-connectors, a compression-crimping tool is recommended. It produces a better, more water-resistant connection than a hex-type crimper.
Punchdown Tool
A punchdown tool (see Figure 11-31) punches the individual wires down into the 110 IDC clips of an RJ-45 jack and the patch panel. This “punching down” of the wires is the actual termination. The patch cables connect the various ports of the patch panel to a switch and the RJ-45 jacks to the computers.
Multimeter
A multimeter is a very flexible tool. It can be used for testing both coaxial and TP cabling as well as AC and DC voltage (see “Multimeter,” p.588, Chapter 13). However, it is easier to test cables with specially made cable testers.
Tone Generator and Probe
The tone generator and probe kit consists of two parts: a tone device, which connects to one end of the network cable and when turned on, sends a tone along the length of the cable; and a probing device, also known as an inductive amplifier, that can pick up the tone anywhere along the cable length and at the termination point. This tool is not as good as a proper network cable tester because it only tests one of the pairs of the wires. However, it is an excellent tool for finding individual phone lines and is more commonly used for that.
Cable Tester
The best option is a proper network cable tester. This device includes a LAN testing unit that you can plug in to a port on the patch panel and a terminator that you plug in to the other end of the cable in the corresponding RJ-45 jack. This tool tests each wire in the cable and makes sure that everyone is wired properly.
Some cable testers, such as the one shown in Figure 11-32, can also be used to test coaxial cable using F-connectors, BNC connectors, or RCA connectors.
Loopback Plug
A loopback plug connects directly to the RJ-45 port of a PC’s network adapter. By using it with a network diagnostic program, it simulates a network and tests whether the network adapter and TCP/IP are functioning properly.
Wi-Fi Analyzer
A Wi-Fi analyzer provides an easy-to-use view of both 2.4 and 5.0GHz wireless networks in your area. You can use a standalone device, a program for your desktop computer, or an app for your Android smartphone.
The InSSIDer Wi-Fi analyzer program for Windows and Mac (www.metageek.com) is a commercial product as of version 4 ($19.95), but free downloads of the previous 3.x version are still available from some download sites, such as MajorGeeks (www.majorgeeks.com) and Softpedia (www.softpedia.com). In Figure 11-33, InSSIDer v3 is displaying both 2.4GHz and 5GHz wireless networks in an office building. Most 2.4GHz networks in this example are using channels 1 or 11, making channel 6 (the only other non-overlapping channel) the best one to use for the selected network. InSSIDer also lists which networks are secure and the MAC address of each router.
You can also use smartphone apps such as WiFi Analyzer (from farproc, on Google Play), the built-in Wireless Diagnostics feature in OS X, and the iwlist command in Linux to learn about the channels used by wireless networks in your vicinity.
Exam Preparation Tasks
Review All the Key Topics
Review the most important topics in the chapter, noted with the Key Topic icon in the outer margin of the page. Table 11-10 lists a reference of these key topics and the page numbers on which each is found.
Complete the Tables and Lists from Memory
Print a copy of Appendix B, “Memory Tables” (found on the CD), or at least the section for this chapter, and complete the tables and lists from memory. Appendix C, “Answers to Memory Tables,” also on the CD, includes completed tables and lists to check your work.
Define Key Terms
Define the following key terms from this chapter, and check your answers in the glossary.
CAT6e
Complete Hands-On Labs
Complete the hands-on labs, and then see the answers and explanations at the end of the chapter.
Lab 11-1: Exploring Wired and Wireless Network Hardware
Examine the physical network in your home, SOHO, or office and determine as much of the following as you can:
TP cable type (5, 5e, 6, and so on). Most cables have the type marked on the protective jacket.
If you have cable Internet service, determine the coaxial cable type.
Does your wireless network use a separate router or is the router built into the cable or DSL modem or fiber gateway?
What is the maximum speed of your wired network? Note: it is the fastest speed supported by all devices. For example, a network with 10/100/1000 (Gigabit) adapters with a 10/100 (Fast Ethernet) switch (or router) runs at Fast Ethernet speeds.
Which wireless standard(s) are supported by your wireless network router? By your wireless adapters?
Lab 11-2: Exploring TCP/IP and Wi-Fi Configuration
Examine the TCP/IP settings in your network and determine as much of the following as you can:
Is your network configured to use DHCP addresses or are some or all devices configured with manual IP addresses?
Do any of your devices use WPS wireless configuration?
Do any of your devices that use DHCP addresses have manual IP addresses set up as alternate addresses?
If you use a wireless network, which type of encryption is used on your network?
If you use WEP encryption, which devices do not support WPA/WPA2 encryption? If you determine that some devices don’t support WPA/WPA2 encryption, determine whether they can be replaced by devices that support WPA/WPA2 encryption to make the wireless network more secure.
Answer Review Questions
1. Complete the following chart with the information provided below.
Answer options:
8-10 microns LED
62.5 microns laser diode
10 Km cable TV, telephone company
60 Km LAN, MAN
2. Which of the following is true of fiber-optic cable as it is compared to twisted-pair or coaxial? (Choose all that apply.)
A. Fiber-optic cable uses light to transmit information.
B. Fiber-optic cable uses high-conductivity copper wire.
C. Fiber-optic cable does not experience crosstalk.
D. Fiber-optic cable is more expensive.
E. Fiber-optic cable is easily installed.
3. Identify the connectors in the following figure.
A. SC duplex fiber
B. ST duplex fiber
C. LC duplex fiber
4. Match the callouts to the terms below to identify these cables and their components;
A. UTP jacket
B. ground wire
C. TP wire pairs
D. TP jacket
E. Metal shield
5. Under which of the following circumstances is a crossover cable used?
A. When connecting one computer to another computer
B. When connecting a computer to a hub
C. When connecting a computer to a patch panel
D. When connecting a computer to a switch
6. Identify the connectors in the following figures.
A. ST
B. RJ-11
C. F-connector
D. AUI
E. BNC
F. LC
G. RJ-45
7. If you need to run network cables through ceiling spaces or air vents, which type of cable should be used?
A. Plenum cable
B. PVC cable
C. Duplex cable
D. Crossover cable
8. Which protocol is used to access the Internet and is used by all major operating systems, including Windows, OS X, Linux, Android, and iOS?
A. APIPA
B. DHCP
C. Telnet
D. TCP/IP
9. 192.168.28.10 is an example of which type of IP address?
A. Class A
B. Class B
C. Class C
D. APIPA
10. Given the IP address of 192.168.28.10, which is the network portion of the address and which is the host portion?
A. 192.=network, 168.28.10=host
B. 192.168. =network, 28.10=host
C. 192.168.28. =network, 10=host
11. Which of the following is the subnet mask for a 192.168.28.10 IP address?
A. 255.255.255.255
B. 255.255.255.0
C. 255.255.0.0
D. 255.0.0.0
12. 127.0.0.1 and ::1 are both IP addresses. Which of the following statements are true? (Choose all that apply.)
A. 127.0.0.1 is a Class A address.
B. ::1 is an IPv6 address.
C. 127.0.0.1 is a Class C address.
D. ::1 is a CIPS address.
E. Both addresses are loopback addresses.
13. 10.0.0.1 is which type of IP address?
A. Public
B. Private
C. APIPA
D. Loopback
14. 169.254.0.1 is which type of IP address?
A. Loopback
B. Subnet mask
C. DHCP
D. APIPA
15. Which of the following statements best describes an advantage of IPv6 over IPv4?
A. IPv6 is less complicated and easier to use.
B. IPv6 automatically assigns IP addresses on a network.
C. IPv6 translates domain names into IP addresses.
D. IPv6 provides a dramatic increase in the number of available IP addresses.
16. Which of the following protocols is used to automatically assign IP addresses on a network?
A. APIPA
B. DHCP
C. TCP/IP
D. DNS
17. In the address www.mycompany.com/locations, which of the following is the top-level domain name?
A. www.
B. .mycompany
C. .com
D. /locations
18. As an IT technician, it is important for you to be familiar with the protocols and ports used by various applications to send and receive information across a network. Complete the following chart by adding the port numbers associated with each of the protocols listed.
19. Which of the following statements best describes SMTP?
A. SMTP is a protocol for sending e-mail from your computer to a server.
B. SMTP is a naming system that links your computer’s name with its IP address.
C. SMTP is a method for automatically assigning IP addresses to computers on a network.
D. SMTP is a protocol used to access the Internet.
20. Which of the following is the family of IEEE standards used by Wi-Fi networks?
A. 802.5
B. 802.11
C. 802.9
D. 802.3
21. Which of the following Wi-Fi encryption methods is the strongest?
A. WPA
B. WPA2
C. WEP
22. Which of the following statements best describes the function of NAT?
A. NAT changes a private IP address for use inside a LAN into a public IP address for use outside a LAN.
B. NAT automatically assigns IP addresses to computers on a LAN.
C. NAT automatically assigns a 169.254.x.x address to a computer on a LAN.
D. NAT is a secure wireless encryption standard.
23. Match the following devices with their definitions.
Converts digital signals to analog and analog signals to digital
Uses a MAC address to direct data to a specific computer
Junction point for network cabling
Allows networks to communicate with each other
Broadcasts data to all attached computers
Connects two LANs
Prevents unwanted intrusion from outside the network
24. Identify the tool in the following figure.
A. Cable tester
B. Crimper
C. Punchdown tool
D. Cable stripper
Answers and Explanations for Hands-On Labs
Complete the hands-on labs, and then see the answers and explanations at the end of the chapter.
Lab 11-1: Exploring Wired and Wireless Network Hardware
When you examine a TP network cable, you might see markings similar to the following:
CAT5E PATCH CABLE
In this example, the cable type is CAT5e (cable markings are usually uppercase).
A coaxial cable might have markings similar to the following:
RG-59/U
RG-6QS
QS = quad shielded (improved shielding to protect the signal quality of HDTV services)
Many vendors who provide Internet and voice service over the same connection include a wireless router in the cable or DSL modem. However, these devices are not as fast and typically have shorter range than mid-range or high-end 802.11ac wireless routers. You can ask the provider to disable the built-in wireless router and provide your own.
To determine the speed of a wired network, you can check the signal lights on each switch port that is connected to a cable. With a Gigabit Ethernet switch, one signal light indicates a connection and the other indicates 1000Mbps (Gigabit) connections. It might use different colors to indicate Gigabit or Fast connections.
Check the label on the wireless router to determine the standards it supports. Check Device Manager in Windows or the comparable utilities on OS X or Linux to determine what wireless network standard(s) their adapters support.
Lab 11-2: Exploring TCP/IP and Wi-Fi Configuration
Devices that have manual IP addresses will not lose their addresses if the DHCP server stops working. However, if the DHCP server is built into the router and the router is shut down or fails, there won’t be any Internet access for any users until it is restored.
WPS wireless configuration should be used for either all devices or no devices. If the network is not already using WPS, don’t use it going forward.
The safest encryption type to use on a wireless network is WPA2 (also known as WPA/AES). Some of the devices that don’t support WPA/WPA2 include some wireless printers and older video game systems with wireless support. If it is not feasible to replace these devices, consider using a separate network for these devices if possible. Then put computers and other devices with sensitive data (tablets, smartphones) on a secure network. Some routers support multiple networks, such as a Guest network.
Answers and Explanations to Review Questions
1.
Single-mode uses a smaller core to carry less information longer distances while multi-mode uses a larger core to carry more information shorter distances.
2. A, C, D. Fiber-optic cables use light instead of electrical signals to transmit information. Because of this, they do not experience electrical interference known as crosstalk and are not susceptible to wire taps and other breaches in security. Fiber-optic cables are also more expensive than twisted-pair or coaxial cables and are more difficult to install.
3. 1–C; 2–B; 3–A. Here is a shortcut to help you remember the names for these connectors. The LC connector has a locking mechanism that clicks the connector into place (LC = lock and click). You stick the ST connector into the port and twist it into position (ST = stick and twist). You stick the SC connector into the port and click it into position (SC = stick and click).
4. A. 4 (UTP jacket); B. 3 (ground wire); C. 5 (TP wire pairs); D. 1 (STP jacket); E. 2 (metal shield).
5. A. Use a crossover cable when connecting two computers to each other. Use a straight-through cable when connecting a computer to a hub, switch, or patch panel.
6. 1-C: F-connector used with cable TV. 2–E: BNC connector used with coaxial cables. 3–B: RJ-11 connector used with CAT 3 telephone cables. 4–G: RJ-45 connector used with Ethernet network cables. Answers A, D, and F were not used.
7. A. Normal network cable is encased in a PVC jacket, which, in case of fire, creates a poisonous thick smoke. Cables that run through ceiling spaces or air vents should be plenum grade, which is more expensive but less toxic if burned.
8. D. TCP/IP is a suite of protocols used for managing traffic on the Internet and is the accepted standard used by all major operating systems.
9. C. 192 is in the Class C range of IP addresses. That means that the first three octets identify the network portion of the address and the fourth octet is the host portion.
10. C. 192 is in the Class C range of IP addresses. That means that the first three octets identify the network portion of the address and the fourth octet is the host portion.
11. B. 255.255.255.0 is the subnet mask for a Class C IP address.
12. B, E. 127.0.0.1 is a diagnostic tool known as the IPv4 loopback address, which is used to test connectivity between a computer and its network. ::1 is the IPv6 counterpart.
13. B. This is an example of a Class A private IP address.
14. D. APIPA addresses are automatically assigned in the event the DHCP system is unable to provide IP addresses. As a technician, any time you see an IP address that begins with 169.254.x.x, you should look for problems with DHCP. APIPA is supported by Microsoft, OS X, and Linux.
15. D. Every device that accesses the Internet (every PC, laptop, notebook, tablet, smartphone, and so on) must have its own IP address—and no two addresses may be the same. In our modern society, a single family might need a dozen addresses; the world is simply running out of IPv4 addresses. IPv6 provides a huge increase in the number of available IP addresses.
16. B. DHCP automatically assigns IP addresses to computers on a network.
17. C. In this example, .com is the top-level domain name. Other examples of top-level domains are .net, .org, and .us.
18.
As an IT technician, you might be called upon to configure ports for a network. The ports in this chart are only a few of the ones you might need to know.
19. A. SMTP is an acronym for Simple Mail Transport Protocol. It is used to send e-mail.
20. B. 802.11 includes 802.11a, 802.11b, 802.11g, 802.11n, and 802.11ac wireless network standards.
21. B. WPA2 uses stronger encryption than WPA. Both WPA and WPA2 have stronger encryption, use longer passphrases, and have other security improvements compared to WEP.
22. A. NAT is a protocol used by a router to change a computer’s private IP address used inside a LAN to a public IP address when communicating outside the network. NAT allows the computers on a LAN to remain hidden from the outside world.
23.
24. B. A crimper is used to attach an RJ-45 or RJ-11 connector to a TP cable.