bgp localpref

Unanswered Question
May 22nd, 2009
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Hi all,


i have 2 routers with in one AS (AS1) and these are connected to 2 seperate TELCO's and my branch office router is connected with both the links.

Our requirement is to have telco1 as primary and telco 2 as secondary.

I have configured local preference at AS1 to influnce the outbound traffic and prepended as-path to influnce the inbound traffic.


But observing out bound traffic from AS1 on both the telcos(not as expected) for location routers and inbound is on telco 1(as expected)


Kindly help

thanks in advance.

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Harold Ritter Fri, 05/22/2009 - 03:44
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Anil,


Do you run iBGP between your routers? If you set the local preference higher on prefixes learned on the session to telco1, there shouldn't be any reason for traffic to exit via telco2 unless your two routers make their own decision (no iBGP).


Regards

anilraahi Fri, 05/22/2009 - 05:32
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also have 2 l3 switches (with hsrp) connected to 2 routers at AS1. and bgp routes are redistribited with equal metric in EIGRP running b/n all 4 devices.

Harold Ritter Fri, 05/22/2009 - 05:57
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Anil,


Are you taking full, partial or only default route from telco1 and telco2?


It is possible that telco2 advertises additional (or more specific) routes that telco1 is not advertising, which would explain why you see some traffic exiting via telco2 even if you run iBGP between your two routers.


Regards

anilraahi Fri, 05/22/2009 - 07:44
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hi all,

have configured route-map at AS1 routers.

telco1 out and telco1 in on one router with prepending AS-path and set local pref respectively and the bgp routes are redistributed in to IGP . and same conf on another router for another telco2.

Regards


ANAND VALMIKI Fri, 05/22/2009 - 13:05
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Run the 'sh ip bgp' command on the telco2 router and verify that you are seeing prefixes from the telco1 router with a higher LP.

anilraahi Fri, 05/22/2009 - 18:56
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hi miki,


no. not getting any prefixes from other routers on both.

Getting routes from same telco as best path with assigned LOCAL PREF.

Harold Ritter Sun, 05/24/2009 - 06:44
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Anil,


Are you certain that the iBGP session is up and running between your two routers?


Can you post the output from a "show ip bgp summary" and your BGP configuration.


Regards

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