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external BGP preference within single routing instance

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  • 1.  external BGP preference within single routing instance

    Posted 11-20-2017 11:25

    Hi,

    I'm setting up a redundant uplink to customer. The idea is to have to physical cables to two core switches (VC).

    Now there is BGP exchange between us. Currently single of this link is active. Both of interfaces are in the same routing instance.

     

    We want to now enable redundancy.

     

    How should we do it ? I was reading a lot about the local-preference value, but as far I understood this applies to iBGP, and we don't have any iBGP here since all is in the same routing-instance and applies to eBGP.

     

    Any ideas ?

     

    Best Regards, 



  • 2.  RE: external BGP preference within single routing instance
    Best Answer

     
    Posted 11-20-2017 14:02

    Local preference will also apply in route selection out to eBGP peers.  You can still use this method to select which of the upstream routes to use.

     

    Assuming you are importing the same routes on both peers, you would just add a term in your import policy to either increment the local preference above 100 for the preferred peer import policy.  Or have a term on the non-preferred import policy that sets local preference less than 100 on routes learned there.

     



  • 3.  RE: external BGP preference within single routing instance

    Posted 11-20-2017 20:47
    As steve mentioned, BGP attribute of local preference is also applicable to E-BGP. You can create an import policy and put the local-preference value less than 100 on the advertizements received from neighbor you want to act as redudant.. FYI..Default value of LP is 100 in BGP advertizements..And higher value of LP is preferred during BGP route selection.