Max age of OSPF LSA's

Answered Question
Mar 24th, 2009

What is the default maximum-age of a Type 1 OSPF LSA? A router with ID 222.1.6.1 is on my multiaccess segment. I was logged on to 222.1.7.1 with log-neighbor-changes enabled; I powered 222.1.6.1 down and watched the adjacency vanish; but the 222.1.6.1 Link ID remained in the output of sh ip ospf database for at least 20 minutes.

How long is it really supposed to stay in there? What's the command to adjust?

I searched Cisco.com for "max-age OSPF" and only got results for Catalyst OS....

I have this problem too.
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Correct Answer by Giuseppe Larosa about 7 years 10 months ago

Hello Stuey,

max-age should be 3600 seconds.

every 1800 seconds the LSA should be refreshed the only one that can do it is the LSA owner.

I've given a look at OSPF command reference and I didn't find any command for changing the max-age

Hope to help

Giuseppe

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Correct Answer
Giuseppe Larosa Tue, 03/24/2009 - 13:31

Hello Stuey,

max-age should be 3600 seconds.

every 1800 seconds the LSA should be refreshed the only one that can do it is the LSA owner.

I've given a look at OSPF command reference and I didn't find any command for changing the max-age

Hope to help

Giuseppe

CriscoSystems Tue, 03/24/2009 - 14:19

Grazie di nuovo, Giuseppe.

So that "every 1800 seconds" thingy is the "paranoid update," eh? But only the LSA owner (you mean originator?) sends it? 'Cause I had thought the paranoid update was when routers synchronize their _entire_ topology table with their neighbors.

I wonder what the purpose is of storing a Type 1 LSA for any length of time when the link is known to be down.

Giuseppe Larosa Tue, 03/24/2009 - 14:39

Hello Stuey,

yes the originator is the LSA owner and the 1800 seconds.

Note: each LSA has its own age so they don't become too old all together.

Anyway the bandwidth usage is very low in comparison to RIP or IGRP.

What you have seen has been reported by other collegues.

My guess is that OSPF is able to detect that the router LSA is not connected anymore to the topology, so instead of having some node to take the role to purge it, it is simply left there to expire in silence.

Hope to help

Giuseppe

the-great-l0k1 Thu, 06/16/2011 - 07:30

you can try under ospf config the next.

router osp 1

timers pacing lsa-group xxx

where xxx is seconds to age-out the LSA..

The-great-l0k1

mx

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