From: Chua, Parry (Parry.Chua@xxxxxxxxxx)
Date: Sun Oct 28 2001 - 22:25:16 GMT-3
Hi,
My understand of the answer is to break the /26 subnet into two /27 subnet
as secondary, since
it has cover by the primary, the secondary is just for redistribute to IGRP,
one of the draw back is the ip address 192.168.1.31 and 192.168.1.32
should not be used as it appear as
network and broadcast for the respective subnet.
> Parry Chua
>
>
-----Original Message-----
From: Hansang Bae [mailto:hbae@nyc.rr.com]
Sent: Monday, October 29, 2001 5:43 AM
To: ccielab@groupstudy.com
Subject: Re: solution: ospf / igrp without using summary-address nor
area range
At 03:35 PM 10/28/01 -0500, Brian Hescock wrote:
>Been pulling yet another all-day / night study session and was going
>through the archive and came across a great solution by Steve Feldberg
>from his posting on 9/24/01, regarding "question on redistribution between
>vlsm and non vlsm". This is a way to get around not being able to use
>summary-address in 12.1 with ospf if the network in question is already in
>ospf and you can't do redistribute connected (and can't use default
>network nor don't want to do local policy on the igrp router to send all
>packets out to the next hop).
>
>His solution is to add secondary ip addresses on an interface with the
>same mask as what is used in igrp. For example, if you have 192.168.1.96
>/27 on the router with igrp and 192.168.1.0 /26 on the ospf router, it's
>not going to work. But if you add secondary ip address on the ospf router
>with "192.168.1.0 255.255.255.224 secondary" and "192.168.1.33
>255.255.255.224 secondary", it works, the 1.0 /27 and 1.32 networks are
>advertised into igrp.
>I verified it on some routers, works great.
This is one of the common ways (ther then summarizing) to get around the
VLSM/NonVLSM issues. But be aware that OSPF will not form adjacency on
secondary addresses. And you have to know the intricacies of what happens
to a routing protocol when secondary addresses are involved.
hsb
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