OSPF Route vía Area0 vs Non-zero

Hello Group,

Can anyone please clarify my doubts in relation to route selected for
non-zero area. Here is the questions;

Q1: R6 in area 1 connected to R1(ABR) that is in area zero via Virtual
Link. R6 is also connected to R4 (ABR) that is the same area 1 and
also area 0. A route from area 2 is learned via R1 and R4. If the
metric of route is lower from R4, does it prefer R4 as a exit point.
As this is learned via are 1 vs area 0 that is R1 route . I always
thought it will prefer route via area 0 that it has learned via R1.

Also capability transit is enabled on Cisco and if you disable this
statement it will forcefully route via area 0 ABR (R1).

Also, it is same affect if R6 has link into Area 0 (non VL) acting as
ABR.

Q2: To calculate overall cost to IA routes, why do we see cost to DR?
If R6 wants to route to IP address in Area 2, I need to check the below:

         1. Cost from ABR to destination IP
         2. Cost from R6 to ABR and also we check DR cost, but if I
have R6 as a DR, why do I need to add cost to myself i.e. R6.

I am confused, or someone explain both scanrios.

Thanks & Regards,
Bilal Hansrod

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Received on Wed Nov 03 2010 - 13:54:25 ART