OSPF Routes

[D Prasanna Kumar Reddy]

Hello All,

What if we get same exact route from two ABRs?? 

From two ASBR ??

One from ABR & One From ASBR ??

Thanks,

Prasanna Kumar Desireddy

[Francesco Molino · Accepted solution]

Hi

The decision made by OSPF for routing is based on route type and cost globally. 

Here is the route selection tie-breaker:

-Intra-area routes.
-Inter-area routes.
-External type 1 routes.
-External type 2 routes.
-Route with the lowest cost if the same type.
-If cost is the same both routes will be installed in the routing table and load balance occurs.

ABR will send LSA type 3 and 4.

ASBR will send LSA type 5 in addition of LSA 3 and 4.

The tiebreaker occurs if you're receiving same type route. However if asbr is sending type 5 (external) while you receive type 3 from abr, type 3 will be preferred. 

Thanks

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