FreeBSD boots too fast on Dell PE850

Patrick M. Hausen hausen at punkt.de
Fri Aug 18 11:33:37 UTC 2006


Hi, all!

On Fri, Aug 18, 2006 at 01:23:15PM +0200, Martin Horcicka wrote:

> Unfortunately, I don't know how it works exactly. In our case when the
> autodetection is disabled and there is e.g. 100/full configured
> manually on both, switch and the FreeBSD box, ifconfig shows the
> interface status wery early as "active". I suspect the switch (Cisco)
> to activate the port (from the point of view of the FreeBSD box) but
> not to forward any "normal" frames until the Spanning Tree Protocol
> procedure is finished for that port. But it's just a guess. I don't
> know the negotiation protocol in Ethernet at all and I would really
> welcome a commentary from someone who does.

This is indeed the case.

The switch port goes up. Then the port goes into either the forwarding
or the blocking state. The transition period usually takes between 30
and 50 seconds, which may be to long for some devices.

spanning-tree portfast puts the port into the forwarding state
immediately but still participates in STP, so eventually a loop
will be detected and the port put back into blocking state again.

The layer 2 interface is, of course, "up" during all this
mumble - otherwise the switch could not send & receive STP frames.
This is what confuses hosts waiting for DHCP or similar.

HTH,

Patrick M. Hausen
Leiter Netzwerke und Sicherheit
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