Network Maintenance

In addition to the TCP/IP set of commands, Solaris provides several network commands that the system administrator can use to check and troubleshoot the network.

Exercise 21.1 Verifying That the Network Is Operational

1.
Check the network’s connection to another system by typing the following:

ping <options> <ip address>

For example, to check the network between systemA and systemB, type ping systemB from systemA. If the check is successful, the remote system replies with this:

systemB is alive

If the network is not active, you get this message:

no answer from systemB

If this is the response, check your cabling and make sure the remote system is configured properly.

2.
Use the snoop utility to determine what information is flowing between systems. The snoop utility can show what actually happens when one system pings another system, as follows:

snoop 192.168.1.106 192.168.1.21

The system responds with the following:

Using device /dev/hme (promiscuous mode) 
192.168.1.106 -> 192.168.1.21 ICMP Echo request (ID: 2677 Sequence number: 0) 
192.168.1.21 -> 192.168.1.106 ICMP Echo reply (ID: 2677 Sequence number: 0)

3.
Check for network traffic by typing the following:

netstat -i 5

The system responds with this:

input   le0   output  input   (Total)  output 
packets errs  packets errs colls packets errs  packets errs colls 
95218   49983 189     1    0     218706  49983 123677  1    0 
0       0     0       0    0     3       0     3       0    0 
0       0     0       0    0     4       0     4       0    0 
1       1     0       0    0     144     1     143     0    0 
0       0     0       0    0     256     0     256     0    0 
0       0     0       0    0     95      0     95      0    0 
0       0     0       0    0     1171    0     1171    0    0

The netstat command is used to monitor the system’s TCP/IP network activity. netstat can provide some basic data about how much and what kind of network activity is happening. The -i option shows the state of the network interface used for TCP/IP traffic. The last option, 5, reissues the netstat command every 5 seconds to get a good sampling of network activity. Press Ctrl+C to break out of the netstat command.

4.
Look in the colls column for a high number of collisions. To calculate the network collision rate, divide the number of output collisions (output colls) by the number of output packets. A network-wide collision rate of greater than 10% can indicate an overloaded network, a poorly configured network, or hardware problems.

5.
Examine the errs column for a high number of errors. To calculate the input packet error rate, divide the number of input errors by the total number of input packets. If the input error rate is high—more than 25%—the host might be dropping packets due to transmission problems. Transmission problems can be caused by other hardware on the network as well as heavy traffic and low-level hardware problems. Routers can drop packets, forcing retransmissions and causing degraded performance.

6.
Type ping -sRv <hostname> from the client to determine how long it takes a packet to make a round trip on the network. If the round trip takes more than a few milliseconds, the routers on the network are slow, or the network is very busy. Issue the ping command twice and ignore the first set of results. The ping -sRv command also displays packet losses. If you suspect a physical problem, use ping -sRv to find the response time of several hosts on the network. If the response time (in milliseconds) from one host is not what you expect, investigate that host.

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