From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Sun Dec 17 2000 - 05:05:54 GMT-3
See Inline...
----- Original Message -----
From: Chuck Larrieu <chuck@cl.cncdsl.com>
To: CCIE_Lab Groupstudy List <ccielab@groupstudy.com>
Sent: Sunday, December 17, 2000 12:21 AM
Subject: Issue Spotting - FLSM and VLSM redistribution
> These are my first looks into the issue of VLSM and FLSM redistribution.
So
> please forgive me if this is a bit of a naïve question.
>
> Practice lab scenario - OSPF and IGRP redistribution
>
> Redistribution router
> -------------------------
> OSPF..............................IGRP
> 172.16.1.0/24................172.16.24.0/24
> 172.16.4.64/26...............172.16.23.0/24
>
> Other OSPF routes from elsewhere
> ----------------------
> 172.16.2.0/24
> 172.16.3.0/24
> 172.16.10.8/30
> 172.16.10.12/30
> 172.16.10.4/30
> 172.16.4.0/26
>
> On the redistribution router, I configure the IGRP process and place the
> 172.16.0.0 network into it. The bad news is that the IGRP domain sees the
> 172.16.1.0 network, even though it shouldn't in that it is supposed to be
> unique in the OSPF domain. The further bad news is that when I do a one
way
> redistribution into the OSPF domain, all OSPF routers can ping interfaces
of
> all routers in the IGRP domain, even though there is no redistribution of
> the OSPF routes into the IGRP domain.
>
> So I start fooling with distribute lists, and proceed to make a mess.
Routes
> disappear. Stop that.
>
> Well, then I do mutual redistribution with no filters. I summarize all my
> longer than /24 routes so they will be redistributed into the IGRP domain.
> Life is good. I can ping all interfaces of either domain from the other.
>
> But something is nagging at me. What did I miss? Is it true that there are
> NO issues in a redistribution scenario if 1) there is only a single point
> of redistribution AND 2) summarization at the IGRP (or any classful
domain)
> occurs at the point of redistribution?
NT: I looked at this the other day and came away thinking along these
lines. In doing
mutual redistribution I walked away thinking that applying a distribute-list
was good practice.
In this scenario one thing stands out above everything else in using these
two specific (IGP's)
IGRP(AD 100) and OSPF(AD 110) the mutual redistribution process. NOTE:That
even if the routes
that was passed to the OSPF domain was redistributed back into the IGRP
domain
the then OSPF routes would not/should not make it to the routing table. The
IGRP domain(routes)
will always have a lower AD on any routes being recieved from the OSPF
domain. Although IGRP does supports 4(default) up to 6 multipath
equal-cost routes wouldn't matter
In contrast if this was a RIP domain this could present a routing loop
because the the
OSPF routes bring redistributed back into the RIP domain would have a lower
AD than
the existing routes.
I'm I making any sense..here or I'm I totally lost in "mass
redistribution..?"
Thoughts.....?
-Nigel
> Thanks for letting me think out loud here.
>
> Chuck
> ----------------------
> I am Locutus, a CCIE Lab Proctor. Xx_Brain_dumps_xX are futile. Your life
as
> it has been is over ( if you hope to pass ) From this time forward, you
will
> study US!
>
>
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