From: Hansang Bae (hbae@xxxxxxxxxx)
Date: Sun Oct 28 2001 - 18:42:40 GMT-3
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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