OSPF with no route Summary??

[mbhandari]

Hi Folks,
Let put some thought.
Network Scenario:

>R3----R1======R2-----R6<
| | ^ |
| | | |
R4-----|-------| |
^ |-------------R5<

R1 & R2 Core router in Area 0
R3,R4,R5,R6 are ABR
&quot;>&quot; show totally Stub Areas.
Q1: What if All ABRs in Area 1 ?
Q2: What will be the ospf Database if networks are such that thay cannot be summerise ?
Q3: Do the Database on R1& R2 will be same as Stub Area (Extn: of Q2)
Q4:How will the Area flooding occur in this Partioned Network.

-bhandari

 

[mbhandari]

Hi,
it seems diagram is little bit distorded. To understand do a cut and paste in reply window and shift R4 till it come under R3 by pressing del key, adjuest other row accordingly.
-bhandari

 

[talisker]

Sorry, but I can't quite figure out your diagram. I'll try to answer your questions though.

First of all it's important to think of interfaces belonging to Areas, not routers. For instance an ABR could have 2 interfaces in Area 1, 1 interface in Area 2 and 4 interfaces in Area 0.

Q1- every ABR has interfaces in at least 2 areas (ie Area 1 & Area 0). It looks like you have a router on each side of Area 0. Therefore at least one router (R6) is an ABR with interfaces in Area 2 & Area 0

Q2-the core routers will have routes to each other & the ABRs, the ABRs will have routes to their internal routers & to the other ABRs and the internal routers will have routes to the other routers in the same area (including the ABR). The totally stubby areas will have no specific routes to other areas or other AS, only a summary default route (0.0.0.0).

Q3-NO. If R1 & R1 are Core routers (all interfaces in Area 0) then they will have routes to all routers with interfaces in Area 0 (each other & the ABRs) and routes to the ABRs representing the other areas (the internal routers of other areas are invisible to am internal router).

Q4-The ABR in Area 1 will advertise to it's internal (stubby)routers &quot;come here if you want to send packets to a host not in this area&quot;, and to other ABRs &quot;come here if you want to send packets to a subnet in Area 1&quot;. The Core Routers will not only advertise &quot;hi, all my interfaces belong in Area 0 and these are the subnets my interfaces belong to&quot;, but they will also have in their database that subnet x.x.x.x is located in area 1, y.y.y.y is located in Area2, etc, because this Area is not stubby.

I hope this helps! B-)