> I have one bgp convergence problem which confused me. The problem is as > follows: > > +--------+ > | AS5 | > +------+16.1/16 | > | +-----+--+ > | | > +---+--+ | > | AS4 | | > | | | > ++-----+ | > | | > | | > | | > +-----+--+ +-+-----+ > | AS2 | | AS3 | 16.1/16 (5) > | ISP | | ISP | > +---^----+ +---^---+ > | | > | +--------+ | > +-----+ AS1 +----+ > |customer| > +--------+ > 16.1/16 (2 4 5) > > AS1 multihomed to AS2 and AS3, for some reasons AS1 disconnect from AS3, > and as a resutl the route to 16.1/16 will be 16.1/16 (2 4 5). > > After a while, the BGP seesion between AS1 and AS3 reestablished but > AS1 leaks the route 16.1/16 (2 4 5) to AS3. At this point, > > 1/ AS1 will have two bgp routes for prefix 16.1/16: 16.1/16(2 4 5)and > 16.1/16(3 5), according to shorter AS_PATH it will select 16.1/16(3 5) > as best route. > > 2/ AS3 also have two bgp routes: 16.1/16(2 4 5) and 16.1/16(5), > according to local_pref it will select 16.1/16(2 4 5). > > in this case, AS1 and AS3 select each other as the best route to AS5, i > wonder which route will be the final best route after bgp convergence in > AS1 and AS3.
this is a bgp wedgie. is it real and caught in the wild? tim would be cheered. randy