Subject: RE: RE: [OSPF] ASBR election

From: "Pradeep BG \(pradg\)" <[email-masked]>
Date: Thu, 18 May 2006 20:46:02 +0530

Attaching Topology map

________________________________

From: Pradeep BG (pradg) 
Sent: Thursday, May 18, 2006 8:45 PM
To: Hasmit Grover (hasmit); 'Pat Murphy - (650)329-4044'
Cc: [email-masked]'
Subject: RE: [OSPF] ASBR election

Area 0 is connected to 2/3 on the SS-3

  

                             2/1
2/1

 

INTERNET

 

Hi

GUYS

WE Are INTERLINKING THIS PROBLEM with another scenario

My question is very simple

Have 3 routers , 2 routers ss-2 and ss-1 they are in area 1(Normal area)
and both of the routers 2/1 link is connected to internet so they are
now ASBR 

have one more router SS-3 which is ABR for area 0 and area 1 , if the 2
routers learn a prefix say (88.88.88.0) , in the routing table of ss-3
what should be displayed

1:whether it should load balance across 2 routers to the destination ?

2:or there is election b/t ss-1 and ss-2 where one router is selected as
the best to forward

3:if yes what is the criteria for selecting the best router

Does RFC say anything for such a problem :-) ?

1:If all the routers are connected through a hub like broadcast access
in the area 1 

or

2: if there is a pt to pt link b/t SS-2 and SS-3 and SS-1 and SS-3

What will be the routing table in ss-3 for both the above questions (how
to reach)

Thanks

-BG

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From: Acee Lindem <[email-masked]>
Date: Fri, 19 May 2006 07:48:14 -0400

Hi Pradeep,

In the future, please do not post MS Word documents to this list. With
respect to your question, RFC 2328 doesn't really say what to do
when you have equal cost paths through the same area. As Pat noted,
RFC 3101 adds the highest router ID as a tie breaker which force
picking the two ASBRs.

However, I can't really see anything magical about a single exit point
for an external route and I would even go so far as to say that it
is an implementation decision (as long as the other path preference
criteria are honored).

Good Luck,
Acee

Pradeep BG (pradg) wrote:

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