Chapter 10
IPv4 and IPv6 Address Management
Objectives
Upon completion of this chapter, you will be able to meet the following objectives:
Describe network boundaries.
Explain the purpose of Network Address Translation in small networks.
Explain why IPv6 addressing will replace IPv4 addressing.
Explain features of IPv6.
Key Terms
This chapter uses the following key terms. You can find the definitions in the Glossary.
Internet of Things (IoT) page 200
Network Address Translation (NAT) page 197
Network Address Translation 64 (NAT64) page 203
Regional Internet Registries (RIRs) page 199
Introduction (10.0.1)
So far, we‛ve talked only about the existence of IPv4 addressing. This chapter explains how IPv4 and IPv6 will coexist in networks for some time to come. It shows you how an IPv6 address is structured and the benefits of IPv6 addressing over IPv4. But the fun part of this chapter is converting binary to hexadecimal notation. Don‛t know what hexadecimal notation is? Read on.
Network Boundaries (10.1)
Routers connect one network to another network. Only devices on separate networks need to forward their packets to a router to be able to communicate.
Video—Gateways to Other Networks (10.1.1)
Refer to the online course to view this video.
Routers as Gateways (10.1.2)
The router provides a gateway through which hosts on one network can communicate with hosts on other networks. Each interface on a router is connected to a separate network.
The IPv4 address assigned to the interface identifies which local network is connected directly to it.
Every host on a network must use the router as a gateway to other networks. Therefore, each host must know the IPv4 address of the router interface connected to the network where the host is attached. This address is known as the default gateway address. It can be either statically configured on the host or received dynamically by DHCP.
When a wireless router is configured to be a DHCP server for the local network, it automatically sends the correct interface IPv4 address to the hosts as the default gateway address. In this manner, all hosts on the network can use that IPv4 address to forward messages to hosts located at the ISP and get access to hosts on the Internet. Wireless routers are usually set to be DHCP servers by default.
The IPv4 address of that local router interface becomes the default gateway address for the host configuration. The default gateway is provided, either statically or by DHCP.
When a wireless router is configured as a DHCP server, it provides its own internal IPv4 address as the default gateway to DHCP clients. It also provides them with their respective IPv4 address and subnet mask, as shown in Figure 10-1.
Figure 10-1 A Router Serving as a Default Gateway
Routers as Boundaries Between Networks (10.1.3)
The wireless router acts as a DHCP server for all local hosts attached to it, either by Ethernet cable or wirelessly. These local hosts are referred to as being located on an internal, or inside, network. Most DHCP servers are configured to assign private addresses to the hosts on the internal network rather than Internet routable public addresses. This configuration ensures that, by default, the internal network is not directly accessible from the Internet.
The default IPv4 address configured on the local wireless router interface is usually the first host address on that network. Internal hosts must be assigned addresses within the same network as the wireless router, either statically configured, or through DHCP. When configured as a DHCP server, the wireless router provides addresses in this range. It also provides the subnet mask information and its own interface IPv4 address as the default gateway, as shown in Figure 10-2.
Figure 10-2 Default Router as Both a DHCP Server and a DHCP Client
Many ISPs also use DHCP servers to provide IPv4 addresses to the Internet side of the wireless router installed at their customer sites. The network assigned to the Internet side of the wireless router is referred to as the external, or outside, network.
When a wireless router is connected to the ISP, it acts like a DHCP client to receive the correct external network IPv4 address for the Internet interface. ISPs usually provide an Internet-routable address, which enables hosts connected to the wireless router to have access to the Internet.
The wireless router serves as the boundary between the local internal network and the external Internet.
Network Address Translation (10.2)
The number of public IPv4 addresses is severely limited, which was one of the primary reasons for RFC 1918 private IPv4 addresses. NAT for IPv4 provides for the translation between private and public IPv4 addresses.
Video—Introduction to NAT (10.2.1)
Refer to the online course to view this video.
NAT Operation (10.2.2)
The wireless router receives a public address from the ISP, which allows it to send and receive packets on the Internet. It, in turn, provides private addresses to local network clients. Because private addresses are not allowed on the Internet, a process is needed for translating private addresses into unique public addresses to allow local clients to communicate on the Internet.
The process used to convert private addresses to Internet-routable addresses is called Network Address Translation (NAT). With NAT, a private (local) source IPv4 address is translated to a public (global) address. The process is reversed for incoming packets. The wireless router is able to translate many internal IPv4 addresses to the same public address by using NAT.
Only packets destined for other networks need to be translated. These packets must pass through the gateway, where the wireless router replaces the private IPv4 address of the source host with its own public IPv4 address.
Although each host on the internal network has a unique private IPv4 address assigned to it, the hosts must share the single Internet-routable address assigned to the wireless router.
In Figures 10-3 and 10-4, a home router translates packets using NAT.
Figure 10-3 Wireless Router Using NAT to Translate Outbound Traffic
Figure 10-4 Wireless Router Using NAT to Translate Inbound Traffic
Packet Tracer—Examine NAT on a Wireless Router (10.2.3)
In this activity, you will complete the following objectives:
Examine NAT configuration on a wireless router.
Set up four PCs to connect to a wireless router using DHCP.
Examine traffic that crosses the network using NAT.
IPv4 Issues (10.3)
IPv4 was designed in the 1970s and implemented in 1980. Since then, the number of devices that access the Internet has increased substantially, beyond the 4.3 billion IPv4 addresses.
Need for IPv6 (10.3.1)
You already know that IPv4 is running out of addresses. That is why you need to learn about IPv6.
IPv6 is designed to be the successor to IPv4. IPv6 has a larger, 128-bit address space, providing 340 undecillion (that is, 340 followed by 36 zeros) possible addresses. However, IPv6 is more than just a larger address space.
When the IETF began its development of a successor to IPv4, it used this opportunity to fix the limitations of IPv4 and include enhancements. One example is Internet Control Message Protocol version 6 (ICMPv6), which includes address resolution and address autoconfiguration not found in ICMP for IPv4 (ICMPv4) and IPv6 addresses (ICMPv6).
The depletion of IPv4 address space has been the motivating factor for moving to IPv6. As Africa, Asia, and other areas of the world become more connected to the Internet, there are not enough IPv4 addresses to accommodate this growth. As shown in Figure 10-5, all five Regional Internet Registries (RIRs) have run out of IPv4 addresses.
Figure 10-5 RIR IPv4 Exhaustion Dates
As noted previously, IPv4 has a theoretical maximum of 4.3 billion addresses. Private addresses, in combination with Network Address Translation (NAT), have been instrumental in slowing the depletion of IPv4 address space. However, NAT is problematic for many applications, creates latency, and has limitations that severely impede peer-to-peer communications.
With the ever-increasing number of mobile devices, mobile providers have been leading the way with the transition to IPv6. The top two mobile providers in the United States report that over 90 percent of their traffic is over IPv6.
Most top ISPs and content providers such as YouTube, Facebook, and Netflix have also made the transition. Many companies like Microsoft, Facebook, and LinkedIn are transitioning to IPv6-only internally. In 2020, US broadband ISP Comcast reported an IPv6 deployment of over 74 percent, and the country of India is now over 62 percent.
Internet of Things
The Internet of today is significantly different than the Internet of past decades. The Internet of today is more than email, web pages, and file transfers between computers. The evolving Internet includes an Internet of Things (IoT). No longer will the only devices accessing the Internet be computers, tablets, and smartphones. The sensor-equipped, Internet-ready devices will include everything from automobiles and biomedical devices to household appliances and lighting systems.
With an increasing Internet population, a limited IPv4 address space, issues with NAT, and the IoT, now is the time to transition to IPv6.
IPv6 Address Size (10.3.2)
IPv6 addressing will eventually replace IPv4 addressing although both types of addresses will coexist for the foreseeable future. IPv6 overcomes the limitations of IPv4 and has features that better suit current and foreseeable network demands. The 32-bit IPv4 address space provides approximately 4,294,967,296 unique addresses.
IPv6 address space provides 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses, or 340 undecillion addresses, which is roughly equivalent to the number of grains of sand on Earth. Table 10-1 provides a visual to compare the IPv4 and IPv6 address space.
Table 10-1 Number of Zeros for Increasing Levels of Scientific Notation
Number Name | Scientific Notation | Number of Zeros |
|---|---|---|
1 Thousand | 103 | 1,000 |
1 Million | 106 | 1,000,000 |
1 Billion | 109 | 1,000,000,000 |
1 Trillion | 1012 | 1,000,000,000,000 |
1 Quadrillion | 1015 | 1,000,000,000,000,000 |
1 Quintillion | 1018 | 1,000,000,000,000,000,000 |
1 Sextillion | 1021 | 1,000,000,000,000,000,000,000 |
1 Septillion | 1024 | 1,000,000,000,000,000,000,000,000 |
1 Octillion | 1027 | 1,000,000,000,000,000,000,000,000,000 |
1 Nonillion | 1030 | 1,000,000,000,000,000,000,000,000,000,000 |
1 Decillion | 1033 | 1,000,000,000,000,000,000,000,000,000,000,000 |
1 Undecillion | 1036 | 1,000,000,000,000,000,000,000,000,000,000,000,000 |
The following are other benefits of the IPv6 protocol:
There is no need for NAT. Each device can have its own globally routable address.
Autoconfiguration capabilities simplify address administration.
The designers of IPv6 thought that it would be adopted quickly, as the number of remaining available IPv4 address blocks was decreasing rapidly. Initial estimates were that IPv6 would be globally deployed by 2003. Obviously, these estimates were incorrect.
Video—Compare IPv4 and IPv6 Addressing (10.3.3)
Refer to the online course to view this video.
IPv4 and IPv6 Coexistence (10.3.4)
There is no specific date to move to IPv6. Both IPv4 and IPv6 will coexist in the near future, and the transition is taking several years. The IETF has created various protocols and tools to help network administrators migrate their networks to IPv6. The migration techniques can be divided into three categories: dual stack, tunneling, and translation.
Dual Stack
Dual stack enables IPv4 and IPv6 to coexist on the same network segment, as shown in Figure 10-6. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously. Known as native IPv6, this means the customer network has an IPv6 connection to its ISP and is able to access content found on the Internet over IPv6.
Figure 10-6 A Dual Stack Topology
Tunneling
Tunneling is a method of transporting an IPv6 packet over an IPv4 network, as shown in Figure 10-7. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data.
Figure 10-7 Routing IPv6 Packets Inside an IPv4 Tunnel
Translation
Network Address Translation 64 (NAT64) enables IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet, and an IPv4 packet is translated to an IPv6 packet. The NAT64 router translates the different IP addresses between networks (the solid line) so that the PCs with different IP addresses can communicate (the dotted line), as shown in Figure 10-8.
Figure 10-8 Translation Between IPv4 and IPv6
IPv6 Features (10.4)
IPv6 is more than just larger address space. A new IP protocol was an opportunity to make performance improvements and provide much-needed new features.
Video—The Hexadecimal Number System (10.4.1)
Refer to the online course to view this video.
Video—Differences Between IPV4 and IPv6 (10.4.2)
Refer to the online course to view this video.
IPv6 Autoconfiguration and Link-Local Addresses (10.4.3)
In addition to the increase in length, IPv6 addresses have other characteristics that are different than IPv4 addresses. Among the differences are the following:
Address autoconfiguration—Stateless Address Autoconfiguration (SLAAC) allows a host to create its own Internet-routable address (global unicast address, or GUA) without the need for a DHCP server. As shown in Figure 10-9, with the default method, the host receives the prefix (network address), prefix length (subnet mask), and default gateway from the Router Advertisement message of the router. The host can then create its own unique interface ID (host portion of the address) to give itself a routable global unicast address.
Figure 10-9 SLAAC Operation
Link-local address—A link-local address is used when communicating with a device on the same network.
The developers of IPv6 made improvements to IP and related protocols such as ICMPv6. These improvements include features related to efficiency, scalability, mobility, and flexibility for future enhancements.
Video—IPv6 Address Representation (10.4.4)
Refer to the online course to view this video.
IPv6 Address Representation (10.4.5)
It is easy for computers to read the new 128-bit IPv6 addressing. IPv6 just adds more ones and zeros to the source and destination addresses in the packet. For humans, though, the change from a 32-bit address written in dotted-decimal notation to an IPv6 address written as a series of 32 hexadecimal digits can be quite an adjustment. Techniques have been developed to compress the written IPv6 address into a more manageable format.
Compressing IPv6 Addresses
IPv6 addresses are written as a string of hexadecimal values. Every 4 bits is represented by a single hexadecimal digit for a total of 32 hexadecimal values. Table 10-2 shows a fully expanded IPv6 address and two methods of making it more easily readable.
Table 10-2 Compressing an IPv6 Address
Fully Expanded | 2001:0db8:0000:1111:0000:0000:0000:0200 |
|---|---|
No leading zeros | 2001:db8:0:1111:0:0:0:200 |
Compressed | 2001:db8:0:1111::200 |
Two rules help reduce the number of digits needed to represent an IPv6 address.
Rule 1: Omit Leading Zeros
The first rule to help reduce the notation of IPv6 addresses is to omit any leading zeros in any 16-bit section. For example, as shown in Table 10-2:
0DB8 can be represented as DB8.
0000 can be represented as 0.
0200 can be represented as 200.
Rule 2: Omit One “All Zero” Segment
The second rule to help reduce the notation of IPv6 addresses is that a double colon (::) can replace any group of consecutive segments that contain only zeros. The double colon (::) can be used only once within an address; otherwise, there would be more than one possible resulting address.
Activity—IPv6 Address Representation (10.4.6)
Refer to the online course to complete this activity.
Lab—Identify IPv6 Addresses (10.4.7)
In this lab, you will complete the following objectives:
Part 1: Identify the different types of IPv6 addresses.
Part 2: Examine a host IPv6 network interface and address.
Part 3: Practice IPv6 address abbreviation.
Summary (10.5)
The following is a summary of each topic in the chapter:
Network Boundaries—The router provides a gateway through which hosts on one network can communicate with hosts on other networks. Each host must know the IPv4 address of the router interface connected to the network where the host is attached. This address is known as the default gateway address. Local hosts are referred to as being located on an internal, or inside, network. The network assigned to the Internet side of the wireless router is referred to as the external, or outside, network. The wireless router serves as the boundary between the local internal network and the external Internet.
Network Address Translation—NAT is used to convert private IP addresses used on an internal network to a public (global) address that can be routed through the Internet. One single public address can be used for many internal hosts.
IPv4 Issues—An IPv4 address is 32 bits (4 bytes) long, meaning there are approximately 4.3 billion IPv4 addresses, which is not enough anymore. The designers of the IP protocols began to become concerned about running out of IPv4 addresses in the early 1990s. In 1993, the IETF started accepting recommendations for enhancements to the IP protocol to support the need for larger address space and to make assigning IP addresses easier for administrators. It took until 1995 for the first IPv6 specification to be published.
An IPv6 address is 128 bits (16 bytes) long, meaning there are enough possible IPv6 addresses to allocate more than the entire IPv4 Internet address space to each person on the planet. IPv6 addressing will eventually replace IPv4 addressing, although both types of addresses will coexist for the foreseeable future. IPv6 does not require NAT, and autoconfiguration capabilities simplify address administration.
Dual stack allows IPv4 and IPv6 to coexist on the same network segment. Dual stack devices run both IPv4 and IPv6 protocol stacks simultaneously. Tunneling is a method of transporting an IPv6 packet over an IPv4 network. The IPv6 packet is encapsulated inside an IPv4 packet, similar to other types of data. Network Address Translation 64 (NAT64) allows IPv6-enabled devices to communicate with IPv4-enabled devices using a translation technique similar to NAT for IPv4. An IPv6 packet is translated to an IPv4 packet, and an IPv4 packet is translated to an IPv6 packet.
IPv6 Features—IPv6 addresses have other characteristics that are different from those of IPv4 addresses:
Address autoconfiguration—SLAAC allows a host to create its own GUA without the need for a DHCP server.
Link-local address—IPv6 addresses can use the link-local address when communicating with a device on the same network.
The developers of IPv6 also made improvements to IP and related protocols such as ICMPv6, including features related to efficiency, scalability, mobility, and flexibility for future enhancements.
IPv6 addresses are written as a string of hexadecimal values. Every 4 bits is represented by a single hexadecimal digit for a total of 32 hexadecimal values. Because of the size of an IPv6 address, techniques have been developed to compress the written IPv6 address into a more manageable format. Two rules help reduce the number of digits needed to represent an IPv6 address:
Rule 1: Omit Leading Zeros—The first rule to help reduce the notation of IPv6 addresses is to omit any leading zeros in any 16-bit section.
Rule 2: Omit One “All Zero” Segment—The second rule to help reduce the notation of IPv6 addresses is that a double colon (::) can replace any group of consecutive segments that contain only zeros. The double colon (::) can be used only once within an address; otherwise, there would be more than one possible resulting address.
Practice
The following activities provide practice with the topics introduced in this chapter.
Labs
Lab—Identify IPv6 Addresses (10.4.7)
Packet Tracer Activities
Packet Tracer—Examine NAT on a Wireless Router (10.2.3)
Check Your Understanding Questions
Complete all the review questions listed here to test your understanding of the topics and concepts in this chapter. Appendix A, “Answers to the ‘Check Your Understanding‛ Questions,” lists the answers.
1. Which statements are correct about IPv4 and IPv6 addresses? (Choose two.)
IPv6 addresses are 32 bits in length.
IPv6 addresses are represented by hexadecimal numbers.
IPv6 addresses are 64 bits in length.
IPv4 addresses are 128 bits in length.
IPv4 addresses are 32 bits in length.
IPv4 addresses are represented by hexadecimal numbers.
2. Which network technology refers to devices that can communicate using both IPv4 and IPv6 addressing at the same time?
Tunneling
SLAAC
NAT64
Dual stack
3. What is an advantage of using IPv6?
More addresses for networks and hosts
More frequencies
Higher bandwidth
Faster connectivity
4. Which characteristic describes the IPv6 default gateway of a host computer?
The physical address of the router interface on the same network as the host computer
The logical IPv6 address of the router interface on the same network as the host computer
The physical address of the switch interface connected to the host computer
The logical IPv6 address assigned to the switch interface connected to the router
5. Which number grouping is a valid IPv6 address?
2001:0db8:3c55:0015:1010::abcd:ff13
2001:0db8::1200::129b
2001:0db8::2001::2900::ab11::1102::0000:2900
2001:0db8::1238::1299:1000::
6. Which method of IPv6 prefix assignment relies on the prefix contained in RA messages?
EUI-64
Stateful DHCPv6
Static
SLAAC
7. Which IPv6 address notation is valid?
2001:db8:a:1111::200
2001:db8:a::1111::200
2001:db8:a:1111:200
2001:db8::::
8. Typically, which network device would be used to perform NAT for a corporate environment?
DHCP server
Router
Switch
Host device
Server
9. What type of IPv6 address is fe80::1?
Multicast
Global unicast
Link-local
Loopback
10. Which network migration technique encapsulates IPv6 packets inside IPv4 packets to carry them over IPv4 network infrastructures?
Encapsulation
Tunneling
Translation
Dual stack