jack daniels wrote:
Hi all ,
I have got a project for an ISP ( also LDP configured ) runnning OSPF to
migrate to IS-IS.
I was planning to runnn dual IGP , as ospf with AD 110 and ISIS with AD 115
, OSPF will always be preffered.
I was planning the challenges for migration, below are the ones which I
could think of , please give your inputs on WHAT CONSIDERATIONS TO KEEP IN
MIND BEFORE MIGRATION.
Also request you to share some docs for migration of OSPF to ISIS<<<<<
1) MEMORY/CPU utilisation
2) no. of routes in routing table and database
3) harware of the cisco devices ( 7206/12K)
Vijay from AOL did such a migration. If memory serves me correctly he
migrated all of AOL in 2 days. Day 1 was the migration of their test
POP. Day 2 was everything in production.
http://www.nanog.org/meetings/nanog29/abstracts.php?pt=Njg2Jm5hbm9nMjk=&nm=nanog29
Here's another NANOG IS-IS presentation.
http://www.nanog.org/meetings/nanog24/abstracts.php?pt=OTA2Jm5hbm9nMjQ=&nm=nanog24
If you search NANOG's resources page you'll find several IS-IS
presentations.
http://www.nanog.org/resources/tutorials/
How many routes does your IGP carry today? Perhaps you should first
move your customer routers into iBGP before you proceed with the IGP
change. That will ensure that your IGP is small. Unless it's extremely
large or your edge routers are on the verge of collapse, I wouldn't
worry about the size too much.
You need to make sure that IS-IS is supported on all your current
platforms. There are some that you may currently utilize that don't
support IS-IS at all. For example most fixed configuration Cat switches
don't support it, though a few do (ME3750 for example). You may need to
bump featuresets to get full IS-IS support in some cases as well so
definitely make use of Cisco's Feature Navigator.
Also, and I'm speaking from my own experience with a thoroughly messed
up OSPF deployment to a flat L2 IS-IS deployment, when you start the
migration don't stop until the migration is complete. Do not leave bits
and pieces of the network unmigrated, assuming that you'll come back
later and fix it. I made that mistake. I guarantee you that dualing
IGPs and/or redistribution will bite you in the ass. There is nothing
quite like the look on one's face when you discover that the routing
between your core routers happens to get routed through a stack of EMI
3750s that is connected to both core routers. Oh yeah. Not pretty.
Don't make the same mistake. Do it Vijay's way; all at once.
Best of luck
Justin
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