Routing

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  • 1.  BGP loop prevention

    This message was posted by a user wishing to remain anonymous
    Posted 10-20-2023 04:59
    This message was posted by a user wishing to remain anonymous

    Hi,

    I tested BGP loop prevention mechanism and as-overwrite in the below case: 

    MX204 - 20.4R3-S3.4

    What I noticed that when R2 is advertising 1.1.1.1 prefix to R3, nothing is visible in the "show route advertising-protocol bgp <R3-PEER-IP> " output on R2. So the 1.1.1.1 routing update is not even sent out from R2 to R3.

    I would expect the 1.1.1.1 route to be propagated to R3 and R3 should drop the prefix once it notices its own "10" AS number in it.  So the receiver should drop the routing update not the sender. How else the "loops" feature for example would be possible otherwise?

    Could you explain this behavior please?



  • 2.  RE: BGP loop prevention

    Posted 10-20-2023 05:12

    On Juniper, by default R2 will suppress them.

    To change the behavior you can use the advertise-peer-as option.

    https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/ref/statement/advertise-peer-as-edit-protocols-bgp.html



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    STUART RIDSDALE
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    Original Message


  • 3.  RE: BGP loop prevention

    Posted 10-20-2023 05:34
    Edited by TAMAS VARGA 10-22-2023 02:14

    Thank you!