Eric, Check out section 3.10.2 of RFC 1195 as I believe it answers your question on why L1 routes are always preferred to L2 routes. There's also additional information in RFC 5302 Section 3.
On Wed, Jun 16, 2010 at 9:56 PM, Eric Van Tol <e...@atlantech.net> wrote: > I do need L2 enabled, as they are the two core routers, and as such, are > the backbone of the network. It's a good suggestion, though. I'll probably > end up just going the static route way, at least until I can swap these out > with two almost-out-of-service Sup720s that can run some decent code. > > As for the L1 route preference, that's what I don't understand. If R1/R2 > are getting each other's loopbacks through L2 with a preference of 18, but > then I swap the L1/L2 preferences so that L2 now has a pref of 15, why would > the L1 route always get preferred? > > -evt > > From: Dan Evans [mailto:pzdev...@gmail.com] > Sent: Wednesday, June 16, 2010 9:05 PM > To: Eric Van Tol > Cc: juniper-nsp > Subject: Re: [j-nsp] ISIS Routing Problem > > Eric, > > Since R1 and R2 are L1/L2 routers they'll each always prefer the L1 route > over the L2 route due to default route preference. It's an interesting > situation for sure. Removing the loopback from L1 isolates R1 and R2 from > advertising their loopbacks to R3 and R4, but with the loopback enabled for > Level 1 you'll always get the long path for R1 to R2 traffic. > > Do you require R1 and R2 to have L2 enabled on the R1--R2 link? You could > turn off L2 on that link and it should give you the result I think you're > expecting. R1 and R2 and still be L1/L2 or L2 only with any other upstream > routers to keep L2 continuity with any routers not in your original > topology. > > > On Wed, Jun 16, 2010 at 7:28 PM, Eric Van Tol <e...@atlantech.net<mailto: > e...@atlantech.net>> wrote: > Hi all, > I'm scratching my head over this one and I'm sure the answer is very > simple. I have four routers: > > R1 --- R2 > | | > | | > R3 --- R4 > > R1 and R2 are L1/L2 routers. R3 and R4 are L1-only routers. Due to IOS's > inability to do MD5 authentication at level 2, I cannot make R3 and R4 L1/L2 > routers. R1 and R2 are running 9.6R3.8. Now the problem... > > I have 'interface lo0.0 passive' configured on both R1 and R2. The > loopback is being injected into the L1 level, then being re-injected back > into the L2 level when it's seen from R3 and R4. I've tried messing with > the preference values for level 2 on R1 and R2, but the loopbacks are always > being preferred through the L1 level. If I configure 'interface lo0.0 level > 1 disable' on R1 and R2, the loopbacks disappear, but then I end up with BGP > recursive route lookups from R3 and R4. I'd prefer not to configure static > routes for the R1 and R2 loopbacks on R3 and R4, but that seems to be my > only recourse at this point. > > Am I missing something simple here or am I just going to have to do the > static routes on R3 and R4, redistribute those between R3 and R4, but deny > their redistribution up to level 2? > > Thanks, > evt > > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net<mailto: > juniper-nsp@puck.nether.net> > https://puck.nether.net/mailman/listinfo/juniper-nsp > > _______________________________________________ > juniper-nsp mailing list juniper-nsp@puck.nether.net > https://puck.nether.net/mailman/listinfo/juniper-nsp > _______________________________________________ juniper-nsp mailing list juniper-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/juniper-nsp