SUMMARY: Transceiver lockups

From: Nigel Titley (
Date: Tue Feb 18 1992 - 05:57:31 CST

We think we have got this one nailed at last (a late night session with
etherfind and a network analyser, yawn.....). We seem to have run for getting
on for a week with no furthur problems.

The trouble is an interaction between PC/NFS and fast Suns. What happens is

1. PC boots up and, because we had not set up a netmask, sends out an "ICMP Mask
Request" broadcast packet.

2. EVERY sun on the network responds with a "Mask Reply". This happens
simultaneously and the resulting confusion and repeated collisions last for
anything up to 2 seconds.

3. One or more transceivers decide that there is a jabbering host on the
network and activate their anti-jabber mode, which effectively locks up the

4. Disconnecting the AUI cable resets the transceiver and it springs back to

The fix is to make sure, with a NET SUBNET xx.xx.xx.xx command on the PC, that
it doesn't make a mask request.

I understand that later releases of PC-NFS try to avoid doing a broadcast mask
request, for this very reason.

Many thanks to all who replied with suggestions, although no one quite hit the
right answer.

Nigel Titley

Snail: British Telecom Research labs, Martlesham Heath, Ipswich, Suffolk, UK
"Well, I'm disenchanted too. We're all disenchanted." (James Thurber)

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