From: Scott Morris (smorris@internetworkexpert.com)
Date: Fri Nov 28 2008 - 00:54:21 ARST
Semantics. :) That is indeed true. It's FASTER, but it just doesn't seem
graceful. Ah well.. But yes, I understand the semantics of that speed!
Scott
-----Original Message-----
From: Marko Milivojevic [mailto:markom@markom.info]
Sent: Thursday, November 27, 2008 4:27 PM
To: Scott Morris
Cc: GAURAV MADAN; Cisco certification
Subject: Re: Graceful shutdown : OSPF
On Thu, Nov 27, 2008 at 19:50, Scott Morris <smorris@internetworkexpert.com>
wrote:
> You could do passive for the interface (in router ospf config), or on
> the interface itself you can use "no routing dynamic"
>
> I'm not sure I'd consider either to be particularly "graceful" though.
They actually are... at least much more than simply shutting down the
interfaces ;-).
It takes time for neighbors and LSA's to be cleared from the tables and run
SPF to recalculate paths and update RIB. If you are using boxes with
separate forwarding plane, it takes even longer! At the same time, CEF table
is intact and router keeps forwarding traffic out the interfaces on which
you disabled OSPF. When recalculation is finished and CEF is updated,
traffic will shift traffic to alternative interfaces, or alternative routers
altogether.
I use this all the time when upgrading backbone nodes.
-- Marko CCIE #18427 (SP) My network blog: http://cisco.markom.info/Blogs and organic groups at http://www.ccie.net
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