On Wed, Jul 10, 2002 at 04:48:30PM -0400, Lupi, Guy wrote: When you say that OSPF scales very well in a heirarchy, I realize that there are a lot of factors involved. Let's assume that all routers in each POP with the exception of aggregation and core are in NSSA areas to control LSA's but still be allowed to insert external routes, but obviously the routers in the core would have to maintain all of the information. How large can you scale a topology like this? I am not concerned so much with the number of routers, but with the number of routes. Are we talking about 8000, 16000, 24000, 40000 routes? I also realize the types of LSA's play a big part in OSPF, but assuming that your aggregation and core routers were very high end Juniper or Cisco routers, what would be a general number using OSPF? ISIS?
In a single ospf instance, and without summarization or stubby/nssa areas, I've seen ~ 4000 subnets. With summarization and/or stubby/nssa areas, I've seen as many as 6000. n.b. - these above numbers are rounded and are examples observed on networks that are comprised of very high end routers. The key is to carry only infrastructure networks in your igp. Minimize infrastructure networks in igp by aggregating (ie, redist a static /24 for all you /30 point-to-point customers). Use bgp to carry customer prefixes. Networks with 16000 routes in igp are probably on the border of resource starvation with hardware that is deployed. Networks with more than 16000 routes in igp are probably doing something like redisting bgp into igp, which is always a bad idea. --phil Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=48539&t=48509 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
