Subject: some clarifications....

From: alok <[email-masked]>
Date: Tue, 4 Feb 2003 13:24:44 +0530

Hi All,

what is the default behaviour of OSPF process on a node A when a neighbour B
and node A loose DD synhcronization?

i mean , i understand the OSPF FSM, but at that point, does it
1. flush all routes which were given by the neighbour and then restart the
whoel thing till the FULL state?
2. retain them till FULL state and flush it only when one enters the "FULL"
state again?

-rgds
Alok

---

From: "Manral, Vishwas" <[email-masked]>
Date: Tue, 4 Feb 2003 07:13:32 -0500

Hi Alok,

If after SPF a route gets deleted, it can also be removed from the RIB.

Once the "adjacency loss" happens, a router changes its router/network LSA.
This in turn causes a change in the routes. The LSA's sent from the "earlier
adjacent router" are not considered, and hence the routes learnt do not
appear in the SPF calculations. Check Section 12.4, RFC2328.

Thanks,
Vishwas

-----Original Message-----
From: alok [mailto:[email-masked]]
Sent: Tuesday, February 04, 2003 4:35 PM
To: [email-masked]
Subject: Re: some clarifications....

Hi,

I think I should restate my question

if the adjacencies are to be reestablished.....  (well, i basically mean the
FSM went back to Exstart state...)

example..router-1 suddenly lost adjacency with router-2...

we have to start allover from the init/exstart state...and we proceed up the
FSM till we get to FULL.

at the time of this "lost  FULL adjacency", while the DD packets and LSRs
and LSUs and LSacks are exchanged:

do the OSPF routes already existing in the "RIB" of router 2 which were
learnt from router 1 get flushed?

what i mean is this:

router-1 is responding to hellos, it exists...but the DB is not
synchronised.

what is the validity of the route on router-2 which was learnt from router-1
by router-2 prior to the loss of adjacency..
is the validity of that old "route" (learnt via some LSA) governed by the
aging time of the previous LSA that router-1 originated?

is this case the same as what happens when the LSrefresh timer expires?

----- Original Message -----
From: Manral, Vishwas <[email-masked]>
To: <[email-masked]>
Sent: Tuesday, February 04, 2003 4:08 PM
Subject: Re: some clarifications....

> Hi Alok,
>
> > what is the default behaviour of OSPF process on a node A when a
neighbour
> B
> You cannot loose DB syncronization, unless you loose your adjacency(as
> flooding in OSPF is relaible). You may however want to check the draft
> http://www.ietf.org/internet-drafts/draft-nguyen-ospf-oob-resync-01.txt.
>
> We never flush routes in OSPF, we flush LSA's. When an adjacency is
lost/new
> adjacency gained, a new router/network LSA is generated the SPF algorithm
> takes care of excluding/including the neighbor from the routing table
> calculation. Check Section 12, RFC2328. We do not the flush other routers
> LSA's.
>
> Thanks,
> Vishwas
>