Weird NFS problems

Skylar Thompson skylar at
Tue May 31 12:58:02 PDT 2005

Jon Dama wrote:

>Yes, but surely you weren't bridging gigabit and 100Mbit before?
>Did you try my suggestion about binding the IP address of the NFS server
>to the 100Mbit side?

Yeah. Unfortunately networking on the server fell apart when I did that. 
Traffic was still passed and I could get through to the server on the 
100Mb/s side, but not on the 1000Mb/s. It looked like the arp tables 
weren't being forwarded properly, but I couldn't convince FreeBSD to do 
proxy arp.

After doing some more poking around, it actually looks like it might be 
a misfeature in the Linux 2.4 kernel wrt ipfilter (which is running on 
the bridge). Apparently 2.4 fragments UDP packets in the reverse order 
that every other UNIX-like operating system does, which throws off 
ipfilter's state tables. I'm going to do some testing to see if the 
difference between UDP and TCP NFS is negligible enough for us to disregard.

Thanks for the suggestions!

-- Skylar Thompson (skylar at

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