Re: ASBR Selection

But that means that OSPF "could" redistribute the route back into EIGRP
since it now has it in it's routing table via OSPF ;-) If EIGRP has a
route that is external (170) and that route is then redistributed into
OSPF (110), never let OSPF install it in the routing table on any router
that is a border router between the OSPF and EIGRP domains. The route is
originally EIGRP right? So you should ensure it's always in the routing
table as an EIGRP route and not via OSPF on routers that are running both
protocols (border routes between the protocol domains).

Cisco has a task almost exactly like yours from their CCIE presentation at
Cisco Live that someone showed me in my last bootcamp. They use the
"classic" route tagging solution to resolve it but I show my students why
the "classic" route tagging solution isn't the best and in fact will not
work in all situations.

Brian Dennis, CCIEx5 #2210 (R&S/ISP-Dial/Security/SP/Voice)
bdennis_at_ine.com
 
INE, Inc.
http://www.INE.com

On 5/28/12 10:16 PM, "Vincent Tay" <vtay.75_at_gmail.com> wrote:

>Hi Mark/Tom,
>
>Thanks. Finally, I have got the concept right. ASBRs (R3 and R2) will not
>have any election. For EIGRP external routes (170), if R3 is the first to
>redistribute, R2 will accept the OSPF routes from R3 since it has higher
>admin distance (110) and its routing table will flush out its EIGRP
>external (170) routes and thus will not be able ro redistribute the routes
>back to R3. This process of operation will happen similarly if R2 is the
>first to redistribute. So, it is a matter on the order of operation
>process. Thanks for the enlightenment.
>
>Data plane path calculation will be base on advertising router and FA if
>present to the ASBR.
>
>Regards
>
>On Tue, May 29, 2012 at 12:52 AM, Marko Milivojevic
><markom_at_ipexpert.com>wrote:
>
>> There is no election. All ASBRs advertise routes that are redistributed.
>> OSPF routers then calculate the best paths to those ASBRs or FA (if
>> present) and chose which routes to use. External metrics are compared
>>first
>> though.
>>
>> --
>> Marko Milivojevic - CCIE #18427
>>
>> :: This message was sent from a mobile device. I apologize for errors
>>and
>> brevity. ::
>>
>> On May 28, 2012, at 1:51, Vincent Tay <vtay.75_at_gmail.com> wrote:
>>
>> > Hi all,
>> >
>> > If there are two ASBRs redistributing routes, will there be any
>> selection?
>> > From what i have try, the router that i clear the ospf process will
>>end
>> up
>> > advertising the type 5 routes. I am quite confuse with it.
>> >
>> > EIGRP
>> > ____________________________________
>> > | |
>> > | |
>> > | |
>> > R3(ASBR)------------------------------R2(ASBR) !
>> > Redistributing EIGRP into OSPF
>> > | |
>> > | |
>> > | |
>> > OSPF Area Routers
>> > ___________________________________
>> >
>> > Thanks.
>> >
>> >
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>> >
>> >
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Received on Tue May 29 2012 - 01:24:15 ART