I've been trying to sort out a routing paradox in my lab and I'm hoping someone might have some insight.
Routers 1-4 are all speaking ISIS-L2. Routers 1,2 originate a default route into ISIS. Routers 1,2 speak MP-iBGP northbound and receive a default route from their respective northbound MP-iBGP sessions. Routers 1,2 redistribute ISIS-L2 routes into MP-iBGP so the north side has reachability. Problem - Because the AD of ISIS is lower than iBGP, R1 and R2 see the ISIS default route an ignore the BGP default route. This causes a routing loop. >From what I've read, it's not possible to apply some sort of filter to the the >ISIS process on R1 or R2 to ignore a learned ISIS default route and just >originate a default route. I can't see any way of adding a route-map to the MP-iBGP sessions on R1 or R2 or either of their northbound MP-iBGP routers to change the AD of the default to less than 115. I can modify the ISIS distance on R1 and R2 to be greater than iBGP, but that would ultimately lead to all ISIS routes on R1/R2 being ignored in favour of the MP-BGP routes for the same destinations being learned from northbound iBGP. Likely more routing loops would ensue here. I could somehow tag the ISIS routes that are redistributed into MP-BGP on R1/R2 and write a route-map to filter those routes from being announced back down to R1 and R2 alleviating the loop. I'm wondering though, is there's a more straightforward answer that I'm not seeing. Thanks in advance. _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
