Strange BGP issue - not advertising BGP route

Answered Question
Jul 17th, 2008

Hi all

I have a strange BGP advertising problem and was hoping that someone might be able to give me an answer.

I run BGP on a Catalyst 3750 switch running Enh Image ver 12.2(25r)SE1. On this switch I've configured BGP v4 on it. A router at a remote office is advertising the following subnets: 10.109.3.0/24; 10.109.5.0/24; 10.109.10.0/24; 10.109.100.0/24 and 10.109.200.0/24 to this Cat3750 switch. It's able to receive all 5 subnets just fine but for some reason, it'll only advertise on the first 4 subnets and not the 5th one on 10.109.200.0/24. I checked the switch and this is what it shows:

#sho ip bgp 10.109.3.0

BGP routing table entry for 10.109.3.0/24, version 1627

Paths: (1 available, best #1, table Default-IP-Routing-Table)

Advertised to update-groups:

2

64900 64900

192.168.157.1 from 192.168.157.1 (10.198.78.36)

Origin IGP, localpref 100, weight 100, valid, external, best

Extended Community: RT:17477:78

#sho ip bgp 10.109.200.0

BGP routing table entry for 10.109.200.0/24, version 1496

Paths: (1 available, best #1, table Default-IP-Routing-Table)

Not advertised to any peer

64900 64900

192.168.157.1 from 192.168.157.1 (10.198.78.36)

Origin IGP, localpref 100, weight 100, valid, external, best

Extended Community: RT:17477:78

The statement "Not advertised to any peer" is clearly the reason for it to not advertise the subnet on to other iBGP peers. I've checked out the link http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800945ff.shtml but it doesn't fix my problem.

Attached is a cut down version of my config and also other show ip bgp xxx commands. Thanks in advance fro your help.

I have this problem too.
0 votes
Correct Answer by Harold Ritter about 8 years 4 months ago

Vincent,

I would try using an outbound route-map instead of a distribute-list and see if the problem goes away.

Regards,

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Overall Rating: 5 (1 ratings)
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arunsing Fri, 07/18/2008 - 00:55

Hi Vincent, There are a few bugs with the 12.2 IOS train that you are using related to BGP. Try clearing the bgp neighborship and see if that fixes the issue.

Harold Ritter Fri, 07/18/2008 - 08:58

Vincent,

I would try using an outbound route-map instead of a distribute-list and see if the problem goes away.

Regards,

Correct Answer
Harold Ritter Fri, 07/18/2008 - 09:01

Vincent,

I would try using an outbound route-map instead of a distribute-list and see if the problem goes away.

Regards,

vincent-n Sun, 07/20/2008 - 15:36

Thank you very much for your post. Implementing a simple route map together with a BGP soft resync has now fixed the problem. The command I used is 'clear ip bgp 10.95.3.19 soft out' just in case someone else is interested.

arunsing Fri, 07/18/2008 - 18:37

Yes I will agree. Infact using route-maps instead of distribute lists is a workaround.

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