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Community Member

Strange BGP issue - not advertising BGP route

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.

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: Strange BGP issue - not advertising BGP route

Vincent,

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

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
5 REPLIES
Community Member

Re: Strange BGP issue - not advertising BGP route

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.

Cisco Employee

Re: Strange BGP issue - not advertising BGP route

Vincent,

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

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Cisco Employee

Re: Strange BGP issue - not advertising BGP route

Vincent,

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

Regards,

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
Community Member

Re: Strange BGP issue - not advertising BGP route

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.

Community Member

Re: Strange BGP issue - not advertising BGP route

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

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