Good FreeBSD question — answering as the UphillTech team:
Since the problem seems isolated to just one interface -- I assume you're using plain old class C masks for these two networks -- I'd just quickly bounce it: # ifconfig en0 down # ifconfig en0 up Obviously you need to substitute the correct interface name here for en0 . You may have to restart any servers listening on that interface, and any established TCP connections using it will drop when you do this. It's brief, though, so I don't really view such a test as "downtime". Be sure not to do this while ssh'd in to the box on the interface you're bouncing. It's best to log in on the console...
Full answer by Warren Young: https://unix.stackexchange.com/a/121 (CC BY-SA 2.5).
Need help with this? UphillTech.