[rescue] What is this traffic?

[Mike Spooner]

Sorry to be late to this thread... from the description of observed
behaviour, this sounds very much like the switch and router have a
disagreement about Ethernet "duplex" mode - during negotiation, one has
picked half-duplex, the other full-duplex, causing a stream of "late
collision" errors on the one using half-duplex mode.

In this situation, I have seen effective throughput drop to 10% of what
should be possible, due to all the errors and semi-synchronised
transmission-backoffs.

If you have access to any kind of "configuration settings" interface on the
router, and that provides a way to change the Ethernet duplex setting on
the "inside" interface, it may well be worth changing that, but be careful
to not cut yourself off if it does not work (ie: use a modern PC directly
conencted to apply the change; don't use a 20+ year-old Sun workstation).

If this resolves the storm, half-duplex-all-over isn't ideal, but should
give you between 50% and 80% of the theoretical throughput (depends a bit
on the exact traffic pattern).

Regards,
Mike