From: Sandro Ciffali (sandyccie@xxxxxxxxx)
Date: Thu Oct 25 2001 - 19:22:46 GMT-3
Stephen,
Certaint things to clarify here,
1)Summary address command under ospf is only to be used for routes being
redistributed from a non ospf routing domain to OSPF routing domain, Not
other wise the way you are using.
2)Still if you use summary address on a ASBR running igrp and ospf routing
subnets of same class B it may work, Not because the command is working but
because of classful nature of igrp.
3)Adding static route to null interface is a right method to redistribute
but will not fetch you marks in the lab. Since no static routes are
allowed.
having said that how would you redistribute a /26 or /27 into /24 igrp??
Here is how I would do it
If the /26 mask exists in the non backbone area you are covered since you
can use area range for the non backbone into backbone as a /24 route and it
goes fine into igrp.
If /26 exists in backbone, I would create a loopback interface with the same
/24 network as this /26, But different /26 (Just to give you an example let
us say your backbone is 10.10.10.128/26, then create a loopback on one of
the abr router a loopback with ip address 10.10.10.65/26) now you can keep
this new loopback in a different area than zero, summarize this network as a
/24 with the range command, Thus your backbone routers will have both /26
and /24 routes out of which /24 will go in igrp.
Hope this helps
Sandro
----- Original Message -----
From: "Stephen Oliver" <stevie_oliver@hotmail.com>
To: <ccielab@groupstudy.com>
Sent: Thursday, October 25, 2001 2:23 PM
Subject: VLSM and IGRP redistribution again.
> Back to my VLSM OSPF into IGRP scenario.
>
> I have a router redistributing OSPF into IGRP and it has /26 and .27
subnets
> on a B class address in the OSPF domain. I wanted to redistribute these
> into IGRP which is running on an interface with a /24 subnet of a B class
> address. So I decided on
>
> # router ospf 1
> # summary-address x.x.x.x 255.255.255.0
>
> Then redistribute into IGRP.
>
> When I type the summary address command the router immediately puts a
route
> to the summary address with next hop null 0 in the routing table. The
route
> is then picked up and advertised correctly into the IGRP domain.
>
> I use three other routers to create the same problem and this time the
> summary address command does NOT install the null route and the routes
never
> get into the IGRP domain. I have to manually install a static route to
null
> 0 then it redistributes ok.
>
> The router that automatically installs the null 0 route runs IOS 11.2(23).
> The router that doesn't runs 12.0(3).
>
> Is there a difference between these two versions in hos they treat the
> summary-address command ?
>
> I've decided the static route to null 0 is the preferable method but I'm
> puzzled as to why the summary-address command works differently on the
> different versions of IOS. Any ideaas ?
>
> Thanks, Stevie.
>
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