John, Vishal

Thanks. I agree that n2 could be advertised as transit network by one that
becomes DR on n2.

However, John, you pointed our cases where n2 may stay as stub. We may have
a reason not to let R1,R2,R3 do normal OSPF process of DR election, DB
exchange etc on interfaces attached to n2.

If n2 is to remain as stubnetwork, other routers will receive r-LSA of
R1, R2, R3 and will find n2 stub network in each of them. How do they keep
information about n2 in their LSDB? How does the routing calculation work
for this?

-Manohar

-----Original Message-----
From: Moy, John [mailto:John.MoySYCAMORENET.COM]
Sent: Friday, January 25, 2002 8:22 AM
To: OSPFDISCUSS.MICROSOFT.COM
Subject: Re: stub network advertising by multiple routes

Manohar-

Vishal's response is correct for the normal case.
And in the normal case, the OSPF spec calls n2 a "transit network",
since it has multiple routers attached and may end up forwarding
traffic that is neither sourced from nor destined for hosts on n2.

However, at times you might see r1, r2 and r3 advertise n2 as a
stub. This could be for one of the following reasons:

a) The DR has not yet been elected (this can take up to
   RouterDeadInterval seconds).
b) The interfaces connecting to n2 have been configured as "passive".
c) The interface parameters in r1, r2, and r3 have been
   configured so that they don't match (Hello Interval, router
   dead interval, authentication type, authentication key). This may
   even be done intentionally so that n2 stays a stub, and doesn't
   get any transit traffic.
d) the DR priority on r1, r2 and r3 has been configured as 0, so
   that n2 never elects a DR. Again, n2 stays a "stub".

John

> -----Original Message-----
> From: Vishal Kumar [mailto:VKumarMAHINETWORKS.COM]
> Sent: Wednesday, January 23, 2002 4:20 PM
> To: OSPFDISCUSS.MICROSOFT.COM
> Subject: Re: stub network advertising by multiple routes
>
>
> r1, r2, r3 will pick a designated router on n2 which will
> originate the
> network LSA.
> r4 doesnt maintain an entry to hosts - packets for hosts with
> ip addresses
> beloning to n2 will be forwarded to the router connected to
> n2 form where
> the router on that lan will deliver the packet to the host. :)
> Cheers!
> -V
>
>
>
> -----Original Message-----
> From: Manohar Naidu Ellanti [mailto:mellantiONI.COM]
> Sent: Wednesday, January 23, 2002 1:06 PM
> To: OSPFDISCUSS.MICROSOFT.COM
> Subject: stub network advertising by multiple routes
>
>
> With a configuration like this:
>
> Host
> |
> |
> ----+--+------+-------+-- N2 (stub network)
> | | |
> R1 R2 R3
> | | |
> ----+-------+-------+----- N1 (normal broadcast network)
> |
> R4
> .........................
>
> Can R1, R2 and R3 advertise N2 as stubnetwork? Or only of
> them should ?
> How R4 and beyond can maintain route entry for host(s) on N2?
>
> -Manohar
>

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]