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  1. Rene,
    Great lesson to understand community. I have question if we have two loopbacks for instance 2.2.2.2/32 on R1 and I would like to advertize this and block 1.1.1.1/32. Do I need an ACL to match under route-map?

    Please confirm
    Hamood

  2. Hi Hamood,

    That's right, in this example I used a really simple route-map but you could do something like this:

    access-list 1 permit host 1.1.1.1
    
    route-map NO_ADVERTISE deny 10
    match ip address 1
    set community no-advertise
    
    route-map NO_ADVERTISE permit 20

    The first route-map statement will deny everything that matches access-list 1, the second route-map statement is required to permit everything else.

    Rene

  3. Hi Rene,

    I am a big fan of you. Thanks for the lessons.
    Follow up the route-map on R1 allowing advertising loopback 2.2.2.2/32 but blocking loopback 1.1.1.1/32 to neigbor BGP router, I found the mistake.

    ip prefix-list LOOPBACK permit 1.0.0.1/32
    !
    route-map SET_NOADVERTISE deny 10    -----------> this should be route-map SET_NOADVERTISE PERMIT 10
     match ip address prefix-list LOOPBACK
     set community no-advertise
    !
    route-map SET_NOADVERTISE permit 20
    !
    router bgp 1
     bgp log-neighbor-changes
     network 1.1.1.1 mask 255.255.255.255
     neighbor 192.168.12.2 remote-as 24
     neighbor 192.168.12.2 send-community
     neighbor 192.168.12.2 route-map SET_NOADVERTISE out

    Can you double-check again Rene?

    Regards,
    Thai

  4. I think the route map with deny statement will deny everything that permitted in access-list statement, so the outbound routes will be filtered if we use the route map with redistribution or with community or any other case, I also check it out with a lab and I see the route 1.1.1.1 in your case will not announce even to R2 !!! If I did not understand, is it possible to clarify this case more ???

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