11-18-2007 03:08 AM - edited 03-05-2019 07:29 PM
If there is a intra-area route to a network that cost more than the inter-area route, is there a preference to choose the higher cost intra-area route over the lower cost inter-area route?
Eg.
Router1(f0/1)-----Area 1-------(f0/0)Router3
|(f0/0)
|
|Area 1
|
|(f0/0)
Router2(f0/1)-----Area 2------(f0/1)Router3
* The Router3 shown above refers to the same router.
Router1 f0/0 and f0/1 are in Area 1.
Router2 f0/0 is in Area 1.
Router2 f0/1 is in Area 2.
Router3 f0/0 is in Area 1.
Router3 f0/1 is in Area 2.
From Router2, to reach f0/0 (Area 1) of Router3, the route will go from Router2->Router1->Router3. Why doesn't it take the shorter path from Router2 to Router3? Is it because the longer route is in the same area and hence is preferred over the shorter inter-area route?
Thanks.
11-18-2007 06:17 AM
In case of OSPF routes, the order of
preference is: (highest to lowest)
Intra area
Inter area
External route type 1 (E1)
External route type 2 (E2)
Within a single ospf process, u cant force the routes to change their preference. This may be possible for routes from different ospf processes.
pls rate if helped.
11-18-2007 06:19 AM
David, not expert in OSPF but there is rule described in RFC-2328 for OSPF route preference, bellow is the order, Intra-area routers are preference over interarea routes
1-intra-area routes, O
2-interarea routes, O IA
3-external routes type 1, O E1
4-external routes type 2, O E2
http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml#q13
HTH
jorge
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