Troubleshooting TCP/IP

Verifying local network connectivity

The ping(1Mtcp) command sends TCP/IP packets to the desired destination and, if successful, returns packets to the sender. With ping, you can verify that the TCP/IP stack is configured correctly on the local host and that your system can reach others via configured interfaces. To verify connectivity:

Enter ping localhost. This routes packets through the loopback mechanism, and should always succeed regardless of the state of your networking hardware or cabling. If it fails, use the Network Configuration Manager to reconfigure TCP/IP.
Verify your network connections by using ping to try to contact one or more hosts on the local network that you know are running TCP/IP. For example, you might enter ping don.

When you ping a remote host, the following results are possible:

The command succeeds, and you see a message similar to:
```
host is alive
```
If ping hangs, you may need to fix interrupt conflicts or netmask/broadcast address problems. Use the Network Configuration Manager to see if the network adapter's hardware settings conflict with those of other hardware in the system. Also verify that the netmask and broadcast address defined for the interface match those of the local network.
If the command succeeds, but slowly and with packet loss, check the network cabling on your system. On an Ethernet network, a loose cable tap, incorrect termination, or poorly placed power cable can result in severely deteriorated service.
If the command fails with the error message ``unknown host'' and you know there is an entry for the host in /etc/hosts, then this file may not have the correct permissions. Use the Software Manager's Verify feature to correct the file's permissions.
A hostname lookup failure may also indicate that a name server used by your host is not running. Contact the administrator of the name server to verify that it is up and running, or see ``Configuring Domain Name System (DNS) servers'', for more information. As a temporary measure, add the IP address and hostname of the system that you are trying to contact to the /etc/hosts file.