From: Bob Sinclair (bsinclair@netmasterclass.net)
Date: Thu May 19 2005 - 15:36:44 GMT-3
San,
RFC 1745 says that when synchronization is enabled and you are redistributing
BGP into OSPF, then the BGP source must also be OSPF ASBR. If they differ,
BGP considers the route un-synchronized.
The basic problem can be satisfied by making sure that the redistribution is
done on the BGP border router, and by assuring that the OSPF RID on that
router is the same as the BGP RID on that router. (which they would be by
default).
The document you reference points out that it is very difficult, if not
impossible, to satisfy the RFC 1745 requirement when you use route-reflectors.
This is because the route-reflector changes the BGP source to the RID of the
route-reflector. If the RR is not the ASBR, you have problems.
As a hack, you can tweak the RIDs so that the OSPF ASBR RID is the same as the
RR RID, even if they are different routers.
HTH,
Bob Sinclair
CCIE #10427, CCSI 30427, CISSP
www.netmasterclass.net
----- Original Message -----
From: san
To: Cisco certification
Sent: Thursday, May 19, 2005 12:37 PM
Subject: BGP basic router-id understanding
Hello Group,
I am trying to understand BGP Notes from 911networks.com. I did not
understand the below points or how to do it . If possible, can you
explain me how to solve it ?
Statement 1:
---------------
The ospf router-id must be the same as the bgp router-id for
redistributing the routes from ospf to bgp. It needs to be done
manually if a route-reflector is involved or it won't work.
Question 1:
----------------
ex: R1---------R2 (RR)------R3
Should i change the router-id of incoming ospf updates on R3 ? or
should i change Bgp router-id on R3 ? Any examples.
Closest i found from searching is below, but could not benefit.
http://www.groupstudy.com/form/read.php?f=7&i=30353&t=30126
Statement 2:
--------------
The BGP Router-id is used with the synchronization and in iBGP the BGP
Router-id is used as tie breaker for the BGP path selection
* Just because the next hop is pingable, it does not mean it's a
valid next hop.
* Next hop addresses that are reachable only via a default route
aren't valid.
* Next hop addresses that are reachable only via another BGP route
are also not valid.
Question 2:
---------------
I thought, if there is a problem with nexthop, route will not be
available in BGP routing table right ?
/SAN
_______________________________________________________________________
Subscription information may be found at:
http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Fri Jun 03 2005 - 10:11:59 GMT-3