From: Sandro Ciffali (sandyccie@xxxxxxxxx)
Date: Sat Mar 16 2002 - 21:28:40 GMT-3
Hackito,
I respectfuly disagree with you. Let us say you have a
router running igrp and ospf both and is using subnets
of a major class B network. Now if you redistribute
ospf and igrp mutualy on this router, Remember igrp is
a class full routing protocol and is running on all
the interfaces of this router, (Even though in the
passive mode). now when you redistribute between ospf
and igrp without using distribute list you are taking
advantage of the fact that ospf has a less admin
distance as compared to igrp and hence everything is
fine, Imagine ospf having larger admin distance than
igrp, Now you will see all the ospf routes as type
external instead of IA or internal.
I think doing redistribution between any two protocols
without reout-map or some kind of filtering has to be
done with filtering no matter you think there is a
route feedback problem or not. Ofcourse these are my
thoughts, you have full rights to disagree with me.
Sandro
--- "Narvaez, Pablo" <Pablo.Narvaez@getronics.com>
wrote:
> I agree with Bob when saying "there is no need to
> configure distribute-lists, route-maps or whatever
> you want to use to avoid route feedback" .... ISn't
> split-horizon supposed to take care of this issue?
> ... The only case I can think of is when you have FR
> in between R2 and R3; if you have a subint
> point-to-point on R2 and you use the physical
> interface on R3 you will have to worry about route
> feedback on R2 since the physical interface on R3
> will have split-horizon disabled ... now you have to
> choose whether you want to use any kind of filter on
> R2 or just enable splithorizon on R3 ...
>
> Please correct me if wrong ... besides, I would like
> to know when I have to worry about route feedback in
> this kind of scenario, with only one way in and out
> for the routes ...
>
> Cheers,
>
> -hockito-
>
>
>
> -----Original Message-----
> From: Bob Sinclair [mailto:bsin@erols.com]
> Sent: Jueves, 14 de Marzo de 2002 09:46 p.m.
> To: Landon Fitts
> Cc: ccielab@groupstudy.com
> Subject: Re: Mutual Redistribution - OSPF / IGRP
>
>
> Landon,
>
> I am sure you will get a lot of feedback on this,
> but let me give you my two cents worth.
>
> The straightforward, text book answer to the problem
> is to create summary routes to null 0 and then
> redistribute these statics into igrp. But I assume
> that option is ruled out.
>
> There has been some discussion of creating a second
> ospf process, redistributing into that to create an
> asbr on R2, then do summary-addresses that can be
> redistributed into igrp. Problem I see here, given
> the ground rules, is that summary address
> automatically creates the null0 routes you are
> trying to avoid. Same thing happens if you create
> an additional ospf area on R2 and do area-range:
> recent IOS automatically creates summaries to null0.
>
> Contrived approach of secondaries does not scale,
> but is only approach that could get the routes there
> with no statics. At least that I see.
>
> My question is: given this scenario, do we have to
> be concerned about route feedback? Why doesn't
> split horizon take care of this? Or are we to
> assume the network might somehow change?
>
> -Bob
>
> ----- Original Message -----
> From: "Landon Fitts" <l.fitts@mindspring.com>
> To: <ccielab@groupstudy.com>
> Sent: Thursday, March 14, 2002 10:05 PM
> Subject: Mutual Redistribution - OSPF / IGRP
>
>
> > I was working on a mutual redistribution scenario
> today between OSPF and
> > IGRP, and a thought came to mind.
> >
> > Here is my scecnario:
> >
> > R1 ------------------ R2-------------------- R3
> > OSPF OSPF | IGRP
> IGRP
> >
> > My OSPF domain has networks that are /30, /29,
> /28,and /24.
> > My IGRP domain has only /24 networks.
> > When I do mutual redistribution at R2 (and use
> distribute-list to prevent
> > route feedback) R1 sees all my IGRP networks, but
> IGRP only sees
> > my /24 networks from OSPF. So, to fix this I used
> the "IP Default-Network"
> > command at R3 pointing to a reachable loopback
> interface
> > in R2 that is part of my ospf domain. Now,
> everybody is happy and all
> > networks are reachable from each router.
> >
> > Now, what I want to know is is "ip
> default-network" considered a static
> > route? If so, what are the other alternatives to
> gain reachability from R3
> > to my other networks that are part of OSPF
> domain. One other possible
> > solution could be to use secondary address between
> R2 and R3, but this isn't
> > scalable because I have several subnets in OSPF.
> >
> > Regards,
> >
> > Landon Fitts
> > NNCSE, NNCDE, CCNP, CCDP, CCIE Lab Candidate
> > l.fitts@mindspring.com
> >
>
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