Re: BGP/OSPF router-id mismatch and the BGP synchronization

Not a problem!

HTH!

On Sat, Feb 13, 2010 at 7:45 AM, Marcel Lammerse <m.lammerse_at_mac.com> wrote:

> Thanks for your quick response Divin :) Just what I was looking for!
>
> Congratulations on passing your CCIE exam. You earned it mate.
>
>
> On 13/02/2010, at 15:15 , Divin Mathew John wrote:
>
> > Check this out. http://www.internetworkexpert.com/rfc/rfc1403.txt
> > 3. BGP Identifier and OSPF router ID
> >
> > The BGP identifier MUST be the same as the OSPF router id at all
> > times that the router is up.
> >
> > This characteristic is required for two reasons.
> >
> > i Synchronisation between OSPF and BGP
> >
> > Consider the scenario in which 3 ASBRs, RT1, RT2, and RT3,
> > belong to the same autonomous system.
> >
> >
> > +-----+
> > | RT3 |
> > +-----+
> > |
> >
> > Autonomous System running OSPF
> >
> > / \
> > +-----+ +-----+
> > | RT1 | | RT2 |
> > +-----+ +-----+
> >
> >
> > Both RT1 and RT2 have routes to an external network X and
> > import it into the OSPF routing domain. RT3 is advertising
> > the route to network X to other external BGP speakers. RT3
> >
> >
> >
> > Varadhan [Page 5]
> >
> > RFC 1403 BGP OSPF Interaction January 1993
> >
> >
> > must use the OSPF router ID to determine whether it is using
> > RT1 or RT2 to forward packets to network X and hence build the
> > correct AS_PATH to advertise to other external speakers.
> >
> > More precisely, RT3 must determine which ASBR it is using to
> > reach network X by matching the OSPF router ID for its route
> > to network X with the BGP Identifier of one of the ASBRs, and
> > use the corresponding route for further advertisement to
> > external BGP peers.
> >
> > ii It will be convenient for the network administrator looking at
> > an ASBR to correlate different BGP and OSPF routes based on
> > the identifier.
> >
> >
> > On Sat, Feb 13, 2010 at 6:16 AM, Marcel Lammerse <m.lammerse_at_mac.com>
> wrote:
> > Hi all,
> >
> > I know this is not common these days, as BGP synchronization is turned
> off by default in recent ios versions. However, I was wondering if anyone
> knows why a Cisco router considers an OSPF route not synchronized, if the
> OSPF router id and BGP router id don't match.
> >
> > Is this an implementation-specfic thing or is there some protocol design
> thinking behind it?
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
> > _______________________________________________________________________
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> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > --
> >
> > Sent from Doha, Qatar
>
>

-- 
Sent from Doha, Qatar
Blogs and organic groups at http://www.ccie.net