I'm looking for a particular AS-PATH regex that match the following case:
"accept ONLY neighbour and it's direct peers".
i.e., my neighbour is AS 20, and has 101, 102 as direct peers.
the as-path "20+ .?" correctly matches the following:
20
20 101
20 102
20 20 20 101
but it does not work if AS 101 is doing AS-prepending (i.e. 20 101 101 101).
Is there a way to achieve that? (if I remember well, in Cisco IOS I can use the \1)
thanks
stefano
Best Answer
This is not possible on JunOS as the AS-Path regular expressions do not support back references (Inserting (part of) a matched expression back into the regular expression itself).