snoop

This command is often used to watch for packets on the network. It must be run as root. It is a good way to make sure that the network hardware is functioning on both the client and the server. Many options are available (see the snoop(1M) man page). A shortened synopsis of the command is given below:

snoop [ -d device ] [ -o filename ] [ host hostname ]

where -d device specifies the local network interface, -o filename stores all the captured packets into the named file, and hostname indicates to display only packets going to and from a specific host.

The -d device option is useful on those servers that have multiple network interfaces. You can use many other expressions besides setting the host. A combination of command expressions with grep can often generate data that is specific enough to be useful.

When troubleshooting, make sure that packets are going to and from the proper host. Also, look for error messages. Saving the packets to a file can make it much easier to review the data.