From: David Clark (dclark@ccbootcamp.com)
Date: Tue Sep 23 2008 - 14:21:37 ART
Incremental SPF allows a router to rebuild only the affected part of the SPT.
Having to recalculate only the changed portion of the SPT results in faster
OSPF convergence and saves CPU resources. However, if the Type 1 or Type 2
link-state advertisement occurs in the calculating router itself , the full
SPT calculation is performed.
Incremental SPF provides greater improvements in convergence time for networks
with a high number of nodes and links, rather than for smaller ones. It also
provides a significant advantage when the changes in the network topology are
further away from the root of the SPT, i.e. the larger the network the more
significant the impact.
Incremental OSPF has been around since 12.0(23)S and was probably not enabled
by default as it uses slightly more memory, however this is not generally a
factor with newer model routers.
________________________________
From: nobody@groupstudy.com on behalf of Igor M.
Sent: Tue 9/23/2008 8:56 AM
To: ccielab@groupstudy.com
Subject: OSPF incremental SPF - ispf option
Hi,
Is anyone aware of the ospf incremental SPF recalculation option under ospf
process? In one of the workbooks I've stumbled on a requirement to make ospf
recalculate its area databases only when there is a change in lsa 1 and lsa 2
types only. They enable ispf under the process:
ispf Enable incremental SPF computation
When would you want to enable this feature and under which circumstances? Why
is it disabled by default?
Thanks!
----------------------
I.M., M.Eng. P.Eng.
Network Architect
CI Investments
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Blogs and organic groups at http://www.ccie.net <http://www.ccie.net/>
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