Re: OSPF ADV Router is not-reachable

Hi Brian

I dont see this OSPF Optimization in Cisco Gear as wel as Juniper box where
the Adjacency goes down adn all teh databases gets flushed immediately. Is
there any special command we need to enable inorder to achieve this.

On Thu, Dec 13, 2012 at 10:15 PM, ccie99999 <ccie99999_at_gmail.com> wrote:

> Thanks Brian,
>
> it's more than clear now!
>
>
>
> On Thu, Dec 13, 2012 at 4:38 PM, Brian McGahan <bmcgahan_at_ine.com> wrote:
>
> > 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
> >
> >
> > --
> > @ccie99999
> >
> >
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-- 
Regards
Hemanth Raj
CCIE#28593 (R&S)
Blogs and organic groups at http://www.ccie.net