No, Chris, the routers receiving a type-3 LSA do NOT need to recalculate the SPF algorithm. The key to understanding this is to realize that the routers within an area have complete knowledge of the topology of the area. In order to get to any destination in a different area, they must go through the ABR. If something changes in another area's topology, it does not affect how they get to the ABR, so no recalculation is required.
Another way to look at it is to recall what information is contained in each type of LSA. Type-1 and type-2 LSAs contain detailed topology information -- not only subnet and mask, but exactly what routers are connected to each of the network(s) in question. The type-3 LSA contains only information about subnets/networks (and their costs) that are reachable through the advertising ABR, not which routers are connected to them. So the topology of an area is invisible to any routers outside that area. If the routers don't have any topology information on an area, there's no information to run SPF against. A foggy reply for early in the morning, but hope this helps a bit. Pamela At 05:21 AM 9/27/01 -0400, "Burnham, Chris" wrote: >Please help. I am a bit confused with the following: > >Summary type 3 LSA's are generated by the ABR for every network and >propogated across area 0. When one of these networks goes down the ABR will >send an update summary LSA to all it's areas ??? If this is the case does >this mean that all SPF routers in all areas will recalculate their SPF >algorithm. > As I understand the whole point of areas is to stop this from >happening? >My question is when an internal router receives a type3 LSA from an ABR >,does it recalculate it's link state database??????????????? >Chris Burnham, >Systems Engineer, >Delphis Consulting Plc. >Tel: +(44) 020 7916 0200 >Mob: +(44) 07799403576 >[EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=21279&t=21273 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
