Ref: 11630009
Title: Red Partition LEDs Suddenly Flash on MultiConnect Repeater
Date: 4/13/90

Copyright 3Com Corporation, 1991.  All rights reserved.

In a network with heavy traffic, all modules in the MultiConnect repeater
may occasionally partition and reconnect without warning.  The condition
is indicated by the flashing of all red partition LEDs (also known as the
"Christmas tree effect").

The DIX and BNC modules should only partition an attached segment if they
think it is faulty, to prevent it from tying up the whole network.  They
partition the segment under these conditions:

  *  if 65 consecutive collisions are detected while transmitting
     (for BNC rev D and above, or DIX rev C and above; else they
     partition if 32 consecutive collisions occur)

  *  if 6.56 milliseconds of carrier are detected on the attached
     segment (indicating an illegally long packet)

  *  if the MultiConnect unit's power supply sagged after power-up.
     (When the module is first powered up, it is brought up in an
     autopartitioned state.  This prevents any potential corrupted
     data from being passed, either from the segment not fully
     operational, or powering up the module in the middle of a packet.)

The "Christmas tree" problem appeared in an early revision of the
gate-array logic (GAL) chips on the BNC and DIX modules, which
caused ALL BNC and DIX modules to partition automatically if any
ONE module detected 6.56 milliseconds of carrier.

To solve the problem, upgrade the BNC modules to rev F and
upgrade the DIX modules to rev E.  Also, check the integrity of
the network, in case the modules actually did detect a faulty
segment.
