From: Lupi, Guy (Guy.Lupi@xxxxxxxxxxxxx)
Date: Wed Mar 27 2002 - 19:25:41 GMT-3
If this is being learned via OSPF and BGP, and the bgp neighbor from which
it was learned is the same as the OSPF neighbor from which it was learned,
then the router ID's have to be the same in BGP and OSPF for it to be
eligible.
>From Cisco:
Paths marked as "not synchronized" in the show ip bgp <longer-prefixes>
output. If BGP synchronization is enabled, which it is by default in Cisco
IOS. Software, there must be a match for the prefix in the IP routing table
in order for an internal (iBGP) path to be considered a valid path. If the
matching route is learned from an OSPF neighbor, its OSPF router ID must
match the BGP router ID of the iBGP neighbor. Most users prefer to disable
synchronization using the no synchronization BGP subcommand.
-----Original Message-----
From: Tarek Sabry [mailto:tsabry@houston.sns.slb.com]
Sent: Wednesday, March 27, 2002 5:07 PM
To: ccielab@groupstudy.com
Subject: BGP - Synchronization
I can get things to work with "no sync", but I was wondering why they are
not otherwise. My understanding is that if the route does exist in the IGP
then it should be OK for advertising. What am I missing?
Below is an illustration for my case for the 88.0.0.0 network.
Thanks
Tarek
r3#sh ip bgp
BGP table version is 1, local router ID is 200.0.0.3
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i8.8.8.0/24 10.10.0.8 0 100 0 i
* i88.0.0.0 10.10.0.8 0 100 0 i
* i192.168.1.0 10.10.0.8 0 100 0 i
* i192.168.2.0 10.10.0.8 0 100 0 i
r3#
r3#
r3#
r3#
r3#sh ip route 88.0.0.0 255.0.0.0
Routing entry for 88.0.0.0/8
Known via "ospf 1", distance 110, metric 65, type inter area
Redistributing via ospf 1
Last update from 10.10.0.8 on Serial0.1, 02:10:35 ago
Routing Descriptor Blocks:
* 10.10.0.8, from 10.10.0.8, 02:10:35 ago, via Serial0.1
Route metric is 65, traffic share count is 1
r3#
r3#
r3#
r3#
r3#sh ip bgp 88.0.0.0
BGP routing table entry for 88.0.0.0/8, version 0
Paths: (1 available, no best path)
Not advertised to any peer
Local, (Received from a RR-client)
10.10.0.8 (metric 64) from 10.10.0.8 (8.8.8.8)
Origin IGP, metric 0, localpref 100, valid, internal, not
synchronized, ref 2
r3#
r3#
-----------------------------------------
Tarek Sabry
Senior Network Engineer
Schlumberger Network Solutions
-----------------------------------------
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