Routing

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  • 1.  Only Community advertisement

    Posted 08-20-2021 08:45
    Hi,

    I have been trying to advertise only the BGP community to a prefix in a new term for a prefix which is already mentioned previously in a term in the same policy statement.

    For example:

    I have a term 

    term1 {
      from { prefix1 }
      then accept
    }



    term 10 {
    from { community match-from-another-bgp-session}
    then { community add community-to-apply}
    }

    I am advertising prefix1 with a BGP community from a different session and I need that session only to advertise community but not to receive the traffic.
    This works when the prefix is being received from a different peer but when the prefix has a static route as discard, the community never gets applied.

    Can anyone help me out with this situation ?

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    ANUSH SHETTY
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  • 2.  RE: Only Community advertisement

     
    Posted 08-23-2021 06:00
    I'm not sure I follow the description, but I think you are noticing that to catch routes that are NOT bgp in a policy then the type of route (static, aggregate, direct) has to be specified in the term.   The default assumption is a bgp route.

    Then in this case you would need to add both bgp and static to the term so you could catch both.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
    http://puluka.com/home
    ------------------------------



  • 3.  RE: Only Community advertisement

    Posted 08-23-2021 17:29

    Hi,

    So what I am trying to achieve is,

    I want to mark an already advertised pool in the term with a BGP community but for the same I do not want to advertise via mentioning it in the term but by an external BGP Peer session.

    For Example, my router has 2 BGP sessions: 

    1) to my upstream
    2) to my Linux Server

    Now I want to advertise a community 1234:1234 to my upstream on a Prefix which is already being advertised via a Term in its respective policy statement.
    The Prefix that is being advertised has its interface in the same router and hence is a Local Route itself.

    So I advertise the community from my Linux Server and that should be passed on to my upstream but I do not want traffic to come to my Linux server.

    But Juniper does not take the route or community in consideration itself when being advertised from my Linux Server because the IP Prefix is attached to the local interface in the router.



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    ANUSH SHETTY
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  • 4.  RE: Only Community advertisement

     
    Posted 08-23-2021 19:37
    Ok, I'm still then not sure I am following this.  So maybe this is wrong too.

    In order to advertise a route to your upstream peer that route has to be active in the table.  It sounds like the active route is the local one and the route received from the server with the community is not active.

    If this active route is a static one, you can add a community to a static route that you create so that it is there and passed on to the upstream too.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
    http://puluka.com/home
    ------------------------------



  • 5.  RE: Only Community advertisement

    Posted 08-23-2021 21:15
    So yes, Active route is a local route.
    Thats my problem actually, I can add the community to the static route but then that has to be done manually.

    I want to attach the community that is coming from my linux server for that prefix despite keeping the static route as the active route.

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    ANUSH SHETTY
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  • 6.  RE: Only Community advertisement

     
    Posted 08-24-2021 05:31
    In that case you need the bgp route to be the active one in the routing table.  So you could manually change the routing preference of the static route to be higher than the bgp route so that it will still be in the table as a backup route but the bgp route that you are learning becomes the active route with its community.

    At that point the bgp route with community would be sent to your other peer.

    ------------------------------
    Steve Puluka BSEET - Juniper Ambassador
    IP Architect - DQE Communications Pittsburgh, PA (Metro Ethernet & ISP)
    http://puluka.com/home
    ------------------------------