Thanks all for sharing information! regards Devang Patel
On Mon, Jan 5, 2009 at 11:43 AM, Justin Shore <[email protected]>wrote: > Kevin Oberman wrote: > >> I would hope you have a backbone well enough secured that you don't need >> to rely on this, but it does make me a bit more relaxed and makes me >> wish we were using ISIS for IPv4, as well. The time and disruption >> involved in converting is something that will keep us running OSPF for >> IPv4 for a long time, though. I remember the 'fun' of converting from >> IGRP to OSPF about 13 years ago and I'd prefer to retire before a >> repeat. >> > > I did the OSPF --> IS-IS migration some time back and here's some of the > info I found at the time. > > > http://www.nanog.org/meetings/nanog29/abstracts.php?pt=Njg2Jm5hbm9nMjk=&nm=nanog29 > > Vijay did a nice presentation on AOL's migration to IS-IS. IIRC AOL > migrated everything in 2 days. Day 1 was to migrate their test POP and hone > their script. All remaining POPs were migrated on Day 2. I believe he said > it went well. There have been several other documented migrations too: > > http://www.geant.net/upload/pdf/GEANT-OSPF-to-ISIS-Migration.pdf > http://www.ripe.net/ripe/meetings/ripe-47/presentations/ripe47-eof-ospf.pdf > > I migrated my SP from a flat OSPF network (end to end area 0) to IS-IS. > The OSPF setup was seriously screwed up. Someone got the bright idea to > changes admin distances on some OSPF speakers, introduce a default in some > places with static defaults in others, redistributing like it was going out > of style, redisting a static for a large customer subnet on P2 instead of P1 > which is what PE1 actually connected to (and not advertising the route from > PE1 for some unknown reason), etc. The old setup was a nightmare. > > The IS-IS migration went fairly well after I got some major bugs worked out > on our 7600s. I implemented IS-IS overtop of OSPF. Some OSPF speakers had > admin distances of 80 and some were default. IS-IS slipped in over top with > no problems. I raised IS-IS to 254 for the initial phase anyway just to be > safe. Once I had IS-IS up I verified it learned all the expected routes via > IS-IS. Then I lowered its admin distance back to the default and bumped > OSPF up to 254. Shortly thereafter I nuked OSPF from each device. It was > hitless. I never could get IS-IS to work with multiple areas. The 7600s > made a smelly mess on the CO floor every time I tried. In the end I went > with a L2-only IS-IS network. Still it works well for the most part. I've > had about as much trouble with IS-IS as I have had with OSPF. Occasionally > some random router will get a burr under it's saddle and jack up the MTU on > the CLNS packets beyond the interface's max. The receiving router will drop > the padded frame as too big. Fixing this can sometimes happen with a > shut/no shut. Sometimes I can nuke the entire IS-IS config and re-add the > config. Other times I simply have to reboot. This doesn't happen too > often; it's usually several hours after I rock the IS-IS boat so to speak. > Still, I wouldn't go back to OSPF for this SP. > > Justin >
