RE: OSPF Route Selection Puzzler

From: Jason T. Rohm (jtrohm@xxxxxxxxxxx)
Date: Wed Apr 03 2002 - 10:47:00 GMT-3


   
Thanks,

That is what I always believed (makes sense), but I coundn't find
documentation to support it (Ok, I was too lasy to spend an hour going
through my OSPF book to find it).

I keep finding these problems with my ccie security labs... the answers show
the router preferring the IA route (but no configuration to do so)...
grrrr....

Jason T. Rohm

-----Original Message-----
From: Peter van Oene [mailto:pvo@usermail.com]
Sent: Wednesday, April 03, 2002 7:27 AM
To: Jason T. Rohm; CCIELIST (E-mail)
Subject: Re: OSPF Route Selection Puzzler

This is the designed behavior of the protocol. Here is an excerpt from
2328.

  Path-type
         There are four possible types of paths used to route traffic to
         the destination, listed here in decreasing order of preference:
         intra-area, inter-area, type 1 external or type 2 external.
         Intra-area paths indicate destinations belonging to one of the
         router's attached areas. Inter-area paths are paths to
         destinations in other OSPF areas. These are discovered through
         the examination of received summary-LSAs. AS external paths are
         paths to destinations external to the AS. These are detected
         through the examination of received AS-external-LSAs.

At 10:06 PM 4/2/2002 -0600, Jason T. Rohm wrote:
>Under what conditions would an OSPF router select a higher cost route over
a
>lower cost route?
>
>Circumstance:
>
>I have a router that is picking a higher cost INTRA-area route over a lower
>cost INTER-area route. I have not changed the administrative distance of
the
>inter-area or intra-area routes.
>
>What would cause this?
>
>-Jason T. Rohm



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