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Default BGP export policy within L3VPN

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  • 1.  Default BGP export policy within L3VPN

    Posted 06-17-2019 03:29

    Hello all,

     

    I'm configuring a L3VPN (VRF) for a customer of ours.

    PPPoE clients enter the L3VPN and are terminated on our router.

    The IP addresses of these PPPoE clients need to be redistributed to a BGP peer configured within this L3VPN.

    My understanding was that these IP addresses (in this case access-internal routes) are being redistributed to all BGP peers when no export policy is configured.

    However, after configuring an 'accept all' policy, I suddenly saw routes being announced to my peer.

     

    https://www.juniper.net/documentation/en_US/junos/topics/concept/policy-routing-policies-actions-defaults.html, says 

    Readvertise all active BGP routes to all BGP speakers, while following protocol-specific rules that prohibit one IBGP speaker from readvertising routes learned from another IBGP speaker, unless it is functioning as a route reflector.

     

    Doesn't this mean that these routes should be re-advertised to my BGP peer?



  • 2.  RE: Default BGP export policy within L3VPN
    Best Answer

     
    Posted 06-17-2019 04:09

    Hello Beeelzebub,

     

    I believe the following statement means that all routes that were received from a BGP peer will be advertised to all other BGP peers unless such advertisement violates BGP rules:

    "Readvertise all active BGP routes to all BGP speakers, while following protocol-specific rules that prohibit one IBGP speaker from readvertising routes learned from another IBGP speaker, unless it is functioning as a route reflector."

     

    In your case, access-internal routes are not BGP routes, and they're not advertised by BGP by default. This is the reason why these routes were advertised to your peer when you configured an export policy with "accept all".

     

    HTH


    Best regards,
    Sergii
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  • 3.  RE: Default BGP export policy within L3VPN

    Posted 06-17-2019 05:07

    Thanks a lot, that's indeed the case here.

    Now I will have to think about an appropriate policy for advertising these routes. An accept all policy would be somewhat broad.



  • 4.  RE: Default BGP export policy within L3VPN

     
    Posted 06-17-2019 05:13

    There are many possible solutions, but it's very inefficient to advertise /32 routes - much better approach is to create static routes for your address pool(s), and then advertise these static routes to your BGP peers.

     

    HTH

     

    Best regards,

    Sergii