Strange log entries

[Tim Wunder]

Hi,
Starting this morning at about 8:08, I've been getting odd entries in 
/var/log/messages. Stuff like:
Jan 21 08:13:30 localserver kernel: NET: 58 messages suppressed.
Jan 21 08:13:30 localserver kernel: neighbour table overflow
Jan 21 08:13:36 localserver kernel: NET: 49 messages suppressed.
Jan 21 08:13:36 localserver kernel: neighbour table overflow
Jan 21 08:13:39 localserver kernel: NET: 39 messages suppressed.
Jan 21 08:13:39 localserver kernel: neighbour table overflow
Jan 21 08:14:05 localserver kernel: NET: 33 messages suppressed.
Jan 21 08:14:05 localserver kernel: neighbour table overflow

A couple of google searches seems to indicate some kind of port scan may 
be happening. Any suggestion on tools to help me find out what's going on?

Thanks,
Tim