OSPF Area0 Vs Non-Zero Area

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.

Regards,

Bilal Hansrod

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Received on Wed Nov 03 2010 - 22:55:46 ART