From: haducbinh (haducbinh@vnpro.org)
Date: Sat Dec 23 2006 - 05:26:56 ART
Thanks Scott!
But I don't understand how to resolve follow problem:
This is topology: R1------R2----R3----R4-----R5
IGP information:
R2,R3,R4: running OSPF
BGP information:
R1 in AS 1000
R5 in AS 5000
R2,R3,R4 in AS 100, must enable synchronyzation all router and R3 is
route-reflector of R2, R4
The problem is: R1 advertise network "X" to R2 via BGP, then R2 redistribute
network "X" to OSPF because of BGP synchronyzation rule, and at R4 received
2 route "X": one via OSPF(with router-id R2) and one via BGP(with router-id
R3). Because of this, route "X" unsyn. So R4 DO NOT advertise route "X" to
R5!
I can not find solution to this situation! Can not change bgp router-id on
R3 equal with ospf router-id on R2 (if we do that, route "X" via BGP on R3
will unsyn).
HaDucBinh
Email: haducbinh@vnpro.org
Y/M: haducbinh
Phone: +84 908 191 322
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-----Original Message-----
From: Scott Morris [mailto:swm@emanon.com]
Sent: Saturday, December 23, 2006 9:50 AM
To: 'haducbinh'; ccielab@groupstudy.com
Subject: RE: BGP Synchronization
Yup, it's right. Says so in the RFC.
I think RFC1403 was the first to lay this out...
"GP 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
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."
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
haducbinh
Sent: Friday, December 22, 2006 2:56 AM
To: ccielab@groupstudy.com
Subject: BGP Synchronization
Hi GS!
Just want to make sure about BGP synchronization work. we have 2 rules
The first:
IBGP learned prefix must have corresponding prefix listed in local
forwarding table if that IBGP prefix is to be advertised to another BGP
speaker.
The second:
The RID of OSPF(ASBR) and RID of advertising IBGP speaker must match when
OSPF is underlying IGP.
The first rule I know how it work!
But the second rule, is it right?
If so, in this case, we have to change RID of IBGP speaker to match with RID
of OSPF router?
Thanks!
HaDucBinh
Email: <mailto:haducbinh@vnpro.org> haducbinh@vnpro.org
Y/M: haducbinh
Phone: +84 908 191 322
---------------------------------------------------------------------------
Vietnamese Professionals (VnPro)
Cisco Authorised Training
149/1D Ung Van Khiem St - Ward 25 - Binh Thanh Dist - HCMC
Tel: (08) 5124257 - (08) 5125314 Fax: (08) 5124314
Website: <http://vnpro.vn> http://vnpro.vn Support Forum:
<http://vnpro.org> http://vnpro.org
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