EXOS 204 TRUNC problem on 4.3BSD Vax

[G.Carpenter%ee.surrey.ac.uk at nsfnet-relay.ac.uk]

We have a Vax 11/750 with an EXOS 204 ethernet card running BSD 4.3
with Sun NFS added to the kernel. The machine is attached to a campus
ethernet comprising mainly Suns, but with Goulds, Masscomps, Primes(!)
and VMS Vaxen running Wollongong TCP/IP.

We occasionally see the message:

vmunix: ex0: receive error=4<TRUNC>

a result of this is that routed takes ex0 (the machines ONLY ethernet
interface) out of the routing tables, so that the machine appears to
be down as far as the network is concerned.

Pinging the Vax also indicates it is dead ( I presume this means that
the ex0 is effectively ifconfig'ed down).

It can usually be fixed by a combination of ifconfig ex0 up and route
add commands, but is clearly a real nuisance, especially since most of
our teaching staff home directories are on the Vax. Occasionally we
have to re-boot.

Looking in /sys/vaxif/if_exreg.h we find the following:

#define	LLRC_TRUNC	0x4	/* pkt received, but truncated to fit buffer */

This is not very helpful to me. Can someone suggest where I should go
from here to find out which buffer, where etc?

Or can someone tell me what the cause of this problem is and how to
fix it?

-- 

Graham Carpenter - G.Carpenter at ee.surrey.ac.uk
Dept of Electronic and Electrical Engineering
University of Surrey, Guildford, Surrey, GU2 5XH.