Path hiding mitigation technique

AS1, AS2, AS3 and AS4 are clients of the route server. AS4 has ADD-PATH rx on.

Only one prefix is used, AS101_pref_ok1, announced by AS101 to AS1 and AS2:

• AS101 -> AS1, AS_PATH = [101]

• AS101 -> AS2, AS_PATH = [101 101 101 101]

The route server has the path toward AS1 as the preferred one.

AS1 announces this prefix to the rs after having added the do not announce to AS3 and do not announce to AS4 BGP communities.

• When mitigation is on, AS3 and AS4 receive the prefix via the sub-optimal path toward AS2.

• When mitigation is off, AS3 does not receive the prefix at all, AS4 receives it because of ADD-PATH capability.