Routing

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Receiving BGP announcements of its own network

  • 1.  Receiving BGP announcements of its own network

    Posted 05-07-2021 05:10
    Hi!

    I have a problem advertising BGP routes and need help.
    One of the routers (R1, MX204) on my network is announcing network /18 to the upstream ISP1:

    # show routing-options
    static {
    route XX.XX.YY.0/18 {
    discard;
    }

    I have a task on another router (R2, SRX300) to advertise network /24 from network /18 to the upstream ISP2.

    # show routing-options
    static {
    route XX.XX.ZZ.0/24 discard;
    }

    run show route advertising-protocol bgp ISP2

    Prefix                             Nexthop           MED       Lclpref            AS path
    * XX.XX.ZZ.0/24         Self                                                             I


    The routers are located in different locations and aren't physically connected.
    Communication between them must be through the ISP providers:

    R1 <---> ISP1 <---> INTERNET <---> ISP2 <---> R2

    Both routers accept announcements of networks that include as-paths of their own autonomous-system,
    but I don't receive routes:

    ----------------------------------------------------
    R1:
    #run show route XX.XX.ZZ.0

    XX.XX.YY.0/18 *[Static/5] 19w2d 18:11:51
    Discard

    ----------------------------------------------------
    R2:
    (address XX.XX.ZZ.1 terminated on the router interface )

    irb {
    unit 500 {
    family inet {
    address XX.XX.ZZ.1/24;
    }
    }

    # run show route XX.XX.YY.0/18

    XX.XX.ZZ.0/24 *[Direct/0] 19:05:29
    > via irb.500
    [Static/5] 6d 20:56:54
    Discard
    XX.XX.ZZ.1/32 *[Local/0] 6d 20:57:05
    Local via irb.500
    ----------------------------------------------------

    I think the problem is that on R1 the network is terminated as static.
    How can i solve this problem?
    Do you need more information?

    Thanks for the help!​​


  • 2.  RE: Receiving BGP announcements of its own network

    Posted 05-08-2021 11:29
    Hi TRFL, this could be a number of things. lets start by verification of a few things.

    is BGP between R1<->ISP1 established? is R1 advertising and receiving routes from ISP1?
    show route advertising-protocol bgp <isp1-ip>
    show route receiving-protocol bgp <isp1-ip>​

    is BGP between R2<->ISP2 established? is R12advertising and receiving routes from ISP2?

    show route advertising-protocol bgp <isp2-ip>
    show route receiving-protocol bgp <isp2-ip>​


    it is typically recommended to not use static in this situation, since static routes can not be retrieved from the routing table even if there is no path to destination - meaning your BGP peer will always advertise /18 regardless. this doesnt seem to be an issue I would say since you only have 1 peer but just fyi. you can replace the /18 static with an aggregate route.
    you are correct! you will need an export policy since routes (static/ aggregate) are external routes.  lets verify your config on both routers. please share the following output as well from both R1, and R2.

    show configuration routing-options
    show configuration protocol bgp group <group-name>

    if any export/import policies used please share these as well:

    show configuration policy-options policy-statement <policy-name>