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Forum Replies

  1. hi Rene,

    couple of doubts on this concept :

    1.
    You said :
    "Removing the private AS number(s) will only work if there are no public AS numbers in the AS path. "
    but we have "2" which is public AS in the path right ? so why did privateAS 64512 got removed after applying the remove-priv-as command.

       Network          Next Hop            Metric LocPrf Weight Path
    *&gt; 1.1.1.1/32       192.168.23.2                           0 <strong>2 64512</strong> i
    1. should ping work from R3 to 1.1.1.1 using config you gave ?

    Thanks

  2. Hi Abhishek,

    It's about the updates that R2 receives from R1, in this AS path you shouldn't see any public AS numbers.

    If you do have any public AS numbers there then the router won't remove them unless you use the remove-private-as all command.

    The ping will not work unless you advertise network 192.168.23.0/24 on R2 or R3 so that R1 can learn it. Otherwise, R1 doesn't know how to reach 192.168.23.3.

    Rene

  3. Hello Rene,
    Great lesson however, I have a question if R3 learns about 1.1.1.1 from R1 then why do we need to remove private AS# command at R2. Please clarify.

    Thanks
    Hamood

  4. Hello Hamood

    R3 learns about 1.1.1.1 from R2. This can be seen in the output from the show ip bgp command executed on R3. The next hop IP is 192.168.23.2 which is that of R2. Also, when BGP neighbour relationships are configured, R3 and R2 are configured to be neighbours.

    So the remove private-as command that's implemented at R2 will have the result of removing the private AS's from BGP updates from R2 to R3.

    As a general rule, the remove private-as command is implemented on the router that is in a public AS but is directly connected to a router in a private AS. This way, private AS's will not be propagated to the Internet.

    I hope this has been helpful!

    Laz

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