Subject: Re: [OSPF] External Path Selection

From: "Nitin Kakkar" <[email-masked]>
Date: Tue, 5 Feb 2008 13:40:12 -0800

IMHO the problem is you are picking area id 2 due to highest area id
check but missing out the fact that its nssa.

If you could check "Highest regular area id"   (Not stub, nssa) you
would have picked area 1 nh, would that create any problem?

Thanks

Nitin

________________________________

From: [email-masked] [mailto:[email-masked]] On Behalf Of
siofedm
Sent: Tuesday, February 05, 2008 4:48 AM
To: [email-masked]
Subject: [OSPF] External Path Selection

Hi,

            I have a problem regarding path selection when there are
multiple paths to ASBR. My topology is as below

   _ _ _ _ _   AREA 2(NSSA)    _ _ _ _ _                         _ _ _ _
_ 

  |                |------------------------|                |   AREA 1
|                 |

  |    RTA    |                                |   RTB
|---------------- |   RTC     |

  |                |------------------------|                |
|                 |

  |_ _ _ _ _|   AREA 1                |_ _ _ _ _|                      |
_ _ _ _ _|

       RTA:  ASBR         RTB: DUT 

 Origination of NSSA LSA into AREA 2 is blocked by configuration. So RTB
I have only external LSAs corresponding the redistribute routes in RTA

 Here my selected path to ASBR RTA is through area 2 (NSSA) (By area-id
comparison). When route calculation is done using the external LSAs, no
nexthops are copied (as

Selected nexthops are through NSSA). So RTB will not install route to
the redistributed destination. But RTC which has path though area 1 to
the ASBR RTA will install the route.

So RTC will forward packets to the redistribute destination but RTB will
drop the packet

Do system administrators configure this type of topology in real time?

If yes, please tell me how to solve this problem,

 

            

Siofed  

K Molvysh

Huawei Technologies

[email-masked]

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