I have a freeBSD 4.9 box that keeps going down every few days and needs to be rebooted. I looked in the dmesg log, and this is being repeated over and over:

arplookup 216.17.32.193 failed: host is not on local network
arplookup 216.17.32.193 failed: host is not on local network
arplookup 216.17.32.215 failed: host is not on local network


What does this mean?

Also, does anyone know where I might be able to better track down the source of the problem? ie, general log files that might indicate what is going on. I dont know if the box is freezing/crashing, or if networking is dying or what.

Here is what some quick googling turned up:
http://www.atm.tut.fi/list-archive/freebsd-stable/msg04815.html

You need to make sure all the machines on the network have the same netmasks or add static routes..

It means the subnet information is incorrect for your IP's, thus your default gatway ( 216.17.32.193 ) appears to not be in the local network.

If you post your ifconfig_* entries from rc.conf we may be able to point out where you went wring.

or if its in a data center on a switch with other machines, someone has a machine plugged in with a wrong ip? its an ip address issue for sure

It usually caused by wrong netmask.
The error is harmless.

It is far from harmless. I would hardly call a server crashing, and non-existent network connectivity to other IPs in the subnet harmless.

I am surprised you can even reach the box and stay connected really..

The error tell you the server cannot connect to the IP listed. The IP is usually within the same network.

It may not be harmless, but I will never call it server crashing.

if you are on a shared switch, someone may have put one of your IP's on their server.