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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. Ciao Rene',

    testing with your topology: if I set no-advertise with a more specific route-map, like:

    ip prefix-list LOOPBACK seq 5 permit 1.0.0.1/32
    !
    route-map SET_NOADVERTISE deny 10
     match ip address prefix-list LOOPBACK
     set community no-advertise
    !
    route-map SET_NOADVERTISE permit 20

    then I get the following result on R2:

    R2#show ip route 1.1.1.1/32
    % Network not in table

    do you have any idea on why is that?

    Regards,
    Salvatore.

  4. Hello Salvatore,

    This should work...1.1.1.1/32 is not in your prefix-list so it should be permitted. I just checked it to be sure and it's working for me.

    Any chance you got the wrong route-map on R1? :slight_smile:

    R1#
    ip prefix-list LOOPBACK permit 1.0.0.1/32
    !
    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

    R2#show ip bgp | include 1.1.1.1
     *>  1.1.1.1/32       192.168.12.1             0             0 1 i

    Rene

  5. 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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