10.10. Troubleshooting Network Connectivity Problems

Problem

You want to troubleshoot network connectivity problems. This is often necessary if a client is experiencing slow logins or network-based failures when accessing resources.

Solution

First, make sure your network adapter is working. Generally there should be a flashing green light to indicate the adapter is connected and transmitting data.

After you've checked the hardware, you can run several command-line tools to aid in troubleshooting connectivity issues. A good first step is to ping the target host, which can tell you if the remote host is reachable and how long it takes to reach it:

> ping <HostNameOrIP>

Here are some of the status messages you can receive from ping:

Reply

The host was reachable.

Request timed out

The target host either did not respond or there is no host configured with the corresponding IP address. You may also see this message if there is a lot of network latency between the two endpoints. You can work around this by using the -w option with ping and specifying the number of milliseconds to wait for each reply.

Unknown host

If you used a DNS name in the ping command, this indicates that the DNS name was not resolvable by the DNS client.

Destination unreachable

The ICMP traffic could not reach the network of the target host. This is often due to a routing problem on an intermediate router or a router being down.

If you've pinged a host and the request timed out or the host was unreachable, a good tool to try ...

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