UNIX System Management: Network connectivity Error Checking

To complete this chapter, you can do the following things:

Use the following command to check http://www.aliyun.com/zixun/aggregation/18415.html "> network connection errors:

Lanscan

Lanadmin

Linkloop

Arp

Ping

Netstat-i

Netstat-a

Netstat-r

Hostname

Nslookup

1. Network Error-checking tool

The following tools are available for network error checking in UNIX:

ARP (BSD)

Ping (public domain)

Netstat (BSD)

Nslookup (BSD)

Traceroute

Using these tools does not necessarily make it clear and straightforward to identify problems with network connectivity. These tools often only give you some hints of questions. You may have to use several tools to find out exactly where the problem is, so you have to have a deep understanding of the network concept and the ability to use every network tool.

2. Potential network connectivity issues

The LAN Terminator is not connected correctly.

Many times, users do not properly abort their LAN cable. There must be two terminators in your network, one at the beginning of the cable and one at the end of the cable.

Nic does not start

If there is a problem with the LAN card, the Ifconfig command fails. If you use an editor, such as VI, to modify a configuration file, a syntax error may occur if you do not pay attention.

IP address error for NIC

There may be an error while configuring the IP_Address in the/etc/rc.config.d/netconf file.

The subnet mask is incorrect

Some people can make an error when configuring the Sumnet_mask in the/etc/rc.config.d/netconf file.

The same IP address has been used by other systems

Sometimes, some people do not apply to the network administrator for a unique IP address when they connect his system to the network.

The routing table is not configured correctly

Some people may have an error in configuring the route parameter in the/etc/rc.config.d/netconf file.

Router down

Sometimes, a system must be shut down, and if you want to shut down a router, you should declare at least two days in advance.

LAN cable is broken

There is a special device to check if a cable is broken.

The length of the LAN is too long to exceed the limit.

If the coaxial cable is installed long before, it is likely that the length of the cable is too long. When a new system is added to the network segment, the problem occurs if the length of the cable exceeds the length limit. The cable inspector can be used to measure the length of the cable.

Hosts file is not configured correctly

If your system cannot resolve a host name to a correct IP address, it may be a problem with your hosts file. If you have two IP addresses (such as a gateway) in your Hosts file, gethostbyname () will only return the first IP address, which may not be the address you want. You should always check your hosts file to ensure correctness.