I know it's lame to reply to my own email but..

I found a way to do this without tweaking the MTU:

Change the sysctl values to the following:

net.inet.tcp.sendspace=3D4096
net.inet.tcp.recvspace=3D4096
net.inet.udp.sendspace=3D4096
net.inet.udp.recvspace=3D4096
net.inet.tcp.rfc1323=3D0

I'll be honest and say I don't know exactly what they do, but I guessed t=
hey=20
were buffer sizes for TCP and UDP, and the last disables large TCP window=
s.

The networking is very solid and seems very responsive now.  Before this =
I=20
could trigger a reboot by serving the "powered by" logo in apache, or try=
ing=20
to scp a large file to another machine.  I'm sure a large ICMP packet cou=
ld=20
still mung the system, so avoid that :)

- Pat

On February 7, 2003 01:09 am, Pat Wendorf wrote:
> Due to the large packet transmit crashing wierdness (I think that's wha=
t it
> is) in the mbe driver, I thought it would be a good idea to kick the MT=
U
> down a notch to see if I could artificially get around the problem.
>
> The interface doesn't seem to support changing MTU size.  The ifconfig =
man
> page states that most interfaces don't support MTU changes.  This seems=
 a
> bit odd coming from the FreeBSD world.  Is MTU tweaking a portability
> issue?
>
> - Pat