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Beginner

BGP route selection

Hi, guys:

I have a quick question. Based on the BGP route selection criteria posted by Cisco, the route with higher local preference is preferred. The route type (EBGP or iBGP) comparison is way down on the list.

So my question is, if an iBGP speaker originated a route by making Local Preference to 200, in the mean while, the local router receives a update from a EBGP peer for the same prefix. In this case, which route does the local router use?

I believe it should use the one from iBGP peer, however, one thing bother me is that the AD value for EBGP route is actually lower than the one for iBGP route, which means, EBGP should be preferred.

Can anybody help me clarify?

Thanks!

cableip

2 REPLIES 2
Cisco Employee

Re: BGP route selection

You are correct in stating that the iBGP learnt path with a local preference of 200 will be choosen over the eBGP learnt path with a lower local preference.

The admin distance doesn't come in to play between BGP learnt paths as the decision is made by BGP according to the best path selection process. The AD would only come into play if the BGP best path was competing with a prefix learnt from another routing protocol (or static) for installation in the RIB.

Hope this helps,

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
Beginner

Re: BGP route selection

Thank you very much, hritter!

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