From: Bob Sinclair (bsinclair@netmasterclass.net)
Date: Thu Jan 08 2004 - 13:51:21 GMT-3
Paul,
AFAIK, there is no comparable "preempt/no preempt" feature int STP. Of
course, you could manally raise the priority of the old root bridge before
restoring it if the outage scenario allows (an IOS upgrade, for example).
You are right to be concerned about the "fail-back" delay. If you run
Uplinkfast on your access switches, for example, then you will get 1-2
second failover to the new root port if the root bridge fails. But when the
root bridge comes back you will have a 30-second outage as the active root
port immediately closes and the new root port goes through listening and
learning.
You could speed this up by tweaking the timers, or you could consider
rapid-pvst+ if all your switches support it.
Bob Sinclair
CCIE #10427, CISSP, MCSE
www.netmasterclass.net
----- Original Message -----
From: "paul" <paul_hwang@hanmail.net>
To: <ccielab@groupstudy.com>
Sent: Thursday, January 08, 2004 10:52 AM
Subject: hsrp and stp (how to avoid second outage)
> HI all,
>
> Assuming that configured the HSRP and STP on the active and standby
> distribution switches.
>
> In case of HSRP, we can use the preemt option to return to the original
> primary switch once the primary switch recovered. That is, without the
> preemp option, secondary switch keeps active continually after the
> primary fails.
>
> Wondering how about the STP.
>
> I configured the PVST+ between Cat6500 and Cat4000 switches.
>
> If the root bridge fails, secondary root bridge will take over to active.
>
> And then, what happen after the original primary swith recovered. I
> understand the original primary switch will regain the root bridge. That
> is, it will bring sencond outage as the HSRP preempt option do. Then how
> can configure the switch so the secondary root bridge keeps the active
> though the original primary returned.
>
> TIA,
>
> Paul.
>
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