Debugging The LAN (Cont.)

Next, we may wish to check the ARP table of both machines. This is done using the 'arp -a' command. Here is a sample output:

? (204.141.72.93) at 00:00:B0:0A:8E:2C [ether] on eth0

We see the host name (or '?' if name lookup revealed no host name), its IP address, its hardware address, and the interface via which our system got this ARP entry.

If we don't see the remote host's address, we might as well check connectivity to other hosts in the LAN. The host that sees other hosts is probably working fine. In this case, we might suspect hardware problems (e.g. loose or disconnected cable, incorrect cable wiring, incompatible network adapter, etc.). We could try to gradually replace each such hardware device, until the connection works.