Subject: Re: trouble with 10baseT autoselect on wm0
To: John Nemeth <email@example.com>
From: Daniel Carosone <firstname.lastname@example.org>
Date: 05/02/2005 09:57:09
Content-Type: text/plain; charset=us-ascii
There are several issues here.=20
The first is STP (802.1d), which affects switch forwarding behaviour.
Ports can be configured to expect no other bridges (with potential STP
loops) with "portfast"; without this they will wait 30s after link is
established before passing traffic, allowing enough time to see STP
packets from any other bridges and resolve the topology. Our
bridge(4) implements this, and can be configured accordingly.
This can commonly be an issue for machines trying to do PXE booting,
which often toggle the link as the reset happens, and times out PXE
BIOS DHCP before the switch goes into forwarding mode again.
It's nothing to do with PHY speed/duplex autonegotiation (Nway),
except that it starts after that has completed. Interoperability
problems in this area used to be more common than they seem to be
these days. If you have to disable this negotiation, remember to set
it manually on *both* ends of the cable.
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