From: Narvaez, Pablo (Pablo.Narvaez@xxxxxxxxxxxxx)
Date: Fri Mar 15 2002 - 13:58:59 GMT-3
I agree with Bob when saying "there is no need to configure distribute-lists, r
oute-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 o
n R2 and you use the physical interface on R3 you will have to worry about rout
e feedback on R2 since the physical interface on R3 will have split-horizon dis
abled ... 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 wor
ry 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 ce
nts worth.
The straightforward, text book answer to the problem is to create summary route
s to null 0 and then redistribute these statics into igrp. But I assume that o
ption is ruled out.
There has been some discussion of creating a second ospf process, redistributin
g into that to create an asbr on R2, then do summary-addresses that can be redi
stributed into igrp. Problem I see here, given the ground rules, is that summa
ry address automatically creates the null0 routes you are trying to avoid. Sam
e 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 cou
ld 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 fe
edback? 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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