spanning tree

Unanswered Question
Jul 16th, 2008

Hi all, with spanning tree, if a port goes up and down will this cause tcn's to be sent out to the whole network, and would this cause each switch to flush its mac address table, or does it reset the mac aging timer to 0 which does the same thing?

cheers

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Francois Tallet Wed, 07/16/2008 - 06:56

A non-edge port (ie a port not configured for portfast) will trigger a topology change. This will eventually lead the cam table to perform fast aging.

RSTP only generates topology changes on non-edge ports going to forwarding, and the result is a flush on most of non-edge ports.

Regards,

Francois

carl_townshend Wed, 07/16/2008 - 07:23

do i still need to setup portfast when using rstp on my edge ports? as I thought rstp does not go through listening and learning states?

cheers

Francois Tallet Wed, 07/16/2008 - 07:25

Yes, it is critical that you identify your edge ports and configure portfast on them.

Regards,

Francois

Francois Tallet Wed, 07/16/2008 - 08:49

It is critical because, not only the port would take 30 seconds to go forwarding at link up (like STP), but also because RSTP or MST sync can revert back this port to discarding any time during a convergence of the backbone. The port would then be again blocked for 30 seconds, and a host behind it would experience worse connectivity to the backbone than with STP:-(

Regards,

Francois

carl_townshend Tue, 07/22/2008 - 11:44

hi

so, by default, without ant extra config using rstp, what is the forward delay? is it the same as normal stp? also what about link type port delays,is this the same?

cheers

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