From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Wed Oct 25 2006 - 23:01:28 ART
Yes when you configure a virtual-link the remote router it
terminates on becomes and ABR. Also you can summarize on just one side
deliberately for the purpose of traffic engineering as well. While not
related to this specific task suppose you have two ABRs between area 0
and area 1 and you are doing the "area 0 range" command on 1 ABR. This
would force traffic to route out the other exit point based on the
longest match routing principle.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Carlos G Mendioroz
> Sent: Wednesday, October 25, 2006 10:38 AM
> To: Gene
> Cc: cyucel@gmail.com; ccielab@groupstudy.com
> Subject: Re: OSPF questions (IE VOL1 LAB7)
>
> Sorry for late update,
> but isn't the case that when you set a virtual link between R5 and R1,
> R1 becomes an ABR ? Then you should place the area range also at R1,
> or else R1 will be injecting the /24 into A1.
> So, I think, it's not R5 the one leaking the information, its R1!
> -Carlos
>
> Gene @ 2/10/2006 10:56 -0500 dixit:
> > Cagri-Try looking at the OSPF database in R3 before and after you
set
> up the virtual link. I think of it like this--if R1 is going to have
an
> interface in area 0 (and the virtual link endpoint is an interface in
area
> 0) then it has to know about everything area 0 knows. In particular,
R1
> needs to know about those unsummarized /24s.So how can R1 find out
about
> those? One way would be to encapsulate the routing updates from R5 to
R1,
> so that R3 doesn't see them. This is the GRE tunnel solution.Another
way
> is to populate R3's database with area 0 information, then pass that
info
> on to R1. This is the way the developers of OSPF chose to implement
> virtual link. So in the virtual link solution R3 sees the /24s.Check
the
> database in R3 with and without the virtual-link and with and without
the
> tunnel.-gt--- On Mon 10/02, Cagri Yucel < cyucel@gmail.com >
> wrote:From: Cagri Yucel [mailto: cyucel@gmail.com]To:
> ccielab@groupstudy.comDate: Mon, 2 Oct 2006 12:27:44 +0100Subject:
>
> > OSPF questions (IE VOL1 LAB7)I am really confused with this one,
below
> is a quick diagramArea 0--------- R5 ---Area1-----R3
------Area1------R1--
> ----Area2Two /24 ranges in area0 are summarised using R5 so they
received
> as a /23 onR3, no problems.Later we add Area2, then naturally a
Virtual
> Link between R5 and R1 fine,suddenly R5 starts to leak /24s to R3.Why
is
> this ? I am not talking about /24s coming from R1 which naturallyneed
to
> be summarised further.IE's solution for the problem is using a tunnel
and
> it works perfectly. Butwhat is the underlying logic ?Why VLINK leaks
> routes at the first place and why tunnel avoids thatbehaviour.-
>
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