RE: OSPF ADV Router is not-reachable

That's normal. This is a convergence optimization of OSPF in which it retains old LSAs until the MAXAGE is reached. The idea is that if the neighbor temporarily flaps, once they come back and they send a database descriptor you will realize that you already have their LSAs in the database from before, and the only thing you need to do is update the neighbor as reachable and reset the age & checksum. Otherwise OSPF would have to go through full flooding every time there is a neighbor flap. If you wait an hour (MAXAGE) you will see the LSA eventually disappear. Normally only the originator of the LSA can prematurely flush the LSA out of the database by reflooding with MAXAGE, and if that router is cut off from the entire OSPF network it cannot flood, hence your case.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com

Internetwork Expert, Inc.
http://www.INE.com

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of ccie99999
Sent: Thursday, December 13, 2012 5:56 AM
To: Cisco certification
Subject: OSPF ADV Router is not-reachable

Hello friends,

I'm working on OSPF in these days and I don't undertand this thing:

I've a stable topology and I've one router (R3) that is my exit point for my nssa area..
R3 indeed is configured as nssa no-summary.
And in the routers in this area (it's area2) get him as only summary LSAs.

                Summary Net Link States (Area 2)

Link ID ADV Router Age Seq# Checksum
0.0.0.0 150.1.3.3 1091 0x80000001 0x00BED9

If now I decide to kill R3 (shut all interfaces) and even do a clear of ospf process, I still see the summary in the ospf database.

If then I check the LSA1 on in it I see ADV Router is not-reachable.

Rack1SW1#show ip ospf database router 150.1.3.3

  Adv Router is not-reachable
  LS age: 2292

I don't understand the reason it's still there. Should't be flushed? and why by design it's not?

thank you

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