Hi Peter, Thanks for the response. Yes, the assumption is that each ABR terminates a single sub-area. The topology supports this assumption.
In a response I was preparing for Chuck's comment, there is one other item I should add-- future service needs might result in the need for TE. I believe the current OSPF specs only supports carrying TE information within an area. Given how OSPF works today, I'd expect that TE would also work, across areas, without the need to carry the actual area ID information. But I'm guessing.... Thanks Peter van Oene wrote: > > Having all sub-areas use the same area-id is functionally possible, but > imposes some key limitations. First off, you can only have ABRs that > terminate 1 sub-area as they have no mechanism for differentiating more > than one. If one were to connect multiple, similarly identified yet > separate areas to the ABR, you would end up with one area thereby defeating > your original goal. This is about the only key limitation I can think of > off hand, but is highly restrictive and certainly overcomes any desire to > optimize config script tools. > > pete > > At 06:12 PM 8/11/2002 m??, bergenpeak wrote: > >Ran across some text in Doyle's V1 that confirms JMcL's comment > >below (page 462, Partioned Areas section). > > > >So, the next question for the group is the following: > > > >OSPF doesn't track the area information once the routing information > >gets injected into the backbone. Suppose you have a network with N > >different physical locations and each will be configured as sub-area. > >Each sub-area connects to the backbone via it's own ABR. > > > >Is there any reason to use different area numbers in this situation? > > > > >From an Ops perspective (say where you have tools to go out and touch > >the configs on the ABR and sub-area routers), using the same area number > >will simplify the configs and tool logic. > > > >So, is there some benefit to actually use different sub-area IDs? > > > >Thanks > > > > > > > > > > > > > bergenpeak wrote: > > > > > > > > Suppose I have two ABRs that are supporting the same sub-area. > > > > The ABRs are not directly connected, but can reach each other > > > > through links inside the sub-area. > > > > > > > > Suppose a link fails causing the two ABRs to not have > > > > connectivity > > > > through the sub-area. The sub-area is therefore partitioned. > > > > > > > > Suppose the ABRs are not doing route summarization. > > > > > > > > Will this cause a problem from the backbone perspective? > > > > > > > > Will this cause a problem for traffic which needs to flow from > > > > one side of the sub-area to the other part of the sub-area? > > > > > > > > Thanks > > > > > > > > > > > > > > I don't believe it will cause any problems. I'm not going to look it up > > > right now, but I'm sure I've researched this one before. As long as > there > > > is no summarisation (or no overlapping summarisation), the two partitions > > > are simply treated as two sub-areas. > > > > > > JMcL Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=51210&t=51210 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
