Hi Jason, You can change AD for default route only.
ip access-list standard ACL-DEFAULT-ROUTE permit 0.0.0.0 router isis distance 240 <R1> 0.0.0.0 ACL-DEFAULT-ROUTE distance 240 <R2> 0.0.0.0 ACL-DEFAULT-ROUTE Kind regards, Bostjan On Wed, Sep 12, 2012 at 7:02 PM, Jason Lixfeld <[email protected]> wrote: > 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/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
