From: steven.j.nelson@xxxxxx
Date: Wed Apr 17 2002 - 04:53:01 GMT-3
Dan
Thanks for this and it works just fine, only one thing.....
I think maybe this is a long winded way of getting this route into a
classfull protocol, you can do the same thing by adding the loopback with
the mask you want to be advertised into rip / igrp (24 in this case) and
then just re distribute connected without the summary address.
This ensures that the /24 mask is seen in IGRP / RIP and any other networks
that have a longer prefix will be matched at the redistributing router, let
me explain myself a bit better
R2----- IGRP ------ R1 ------OSPF NETWORK
R1 is receiving a E2 route from a neighbour with the mask 172.23.0.0 / 18,
this cannot go into igrp as this so we need to summarise this to /16
So I create a loopback with the address of 172.23.29.1 255.255.0.0 (Not used
anywhere else in the network) and then redsitribute connected into ospf,
then ospf to IGRP
The / 16 net shows up in IGRP and when you try to connect to a device on the
/18 subnet the router (r1) has a more specific route and sends the traffic
accordingly.
Does this make sense.
Thanks for your help.
Steve
-----Original Message-----
From: DAN DORTON [mailto:DHSTS68@dhs.state.il.us]
Sent: 16 April 2002 17:02
To: tsabry; dan_schaw
Cc: ccielab
Subject: RE: OSPF - IGRP
Let say you have a range of 172.168.1.0/28 in ospf that you need to get into
a 172.168.2.0/24 IGRP, or RIP domain.
Summary-address only works INTO ospf right?
You need to make this 172.168.1.0/28 network into a 172.168.1.0/24 network
to overcome the rip/igrp domains classful boundry problems right?
Create a loopback with address 172.168.1.17/28 at your ASBR.
Do not advertise this network into OSPF.
Instead create a route-map to permit it.
access-list 1 permit 172.168.1.16 0.0.0.15
route-map con2ospf permit 10
match ip address 1
Then create a summary address under ospf.
router ospf 1
summary-address 172.168.1.0 255.255.255.0
Then redistribute connected INTO ospf with the route-map.
router ospf 1
redistribute connected subnets route-map con2ospf
Since 172.168.1.16/28 network fits into the summary-address range of
172.168.1.0/24 ospf will create a route to null 0 for the 172.168.1.0/24
network.
Because connecteds being redistributed INTO ospf are external networks the
summary-address works.
Because 172.168.1.0/28 & 172.168.1.16/28 both fit into the major network
172.168.1.0/24 the summary-address will work to reach both networks.
Because 172.168.1.0/24 route matches the 172.168.2.0/24 network on the
igrp/rip domain at the classfull 172.168.0.0/16 & the mask of /24 which is
on the igrp/rip domain the igrp/rip domain will accept the summary route.
Hope this helps everyone.
Dan
>>> Tarek Sabry <tsabry@houston.sns.slb.com> 04/16/02 10:10AM >>>
Muhammad
Thanks for your reply.
I fully agree that summary-address is for injecting a summary INTO OSPF and
not to redistribute into another protocol. But I've seen people using it
otherwise :( Is this IOS-related?
How can I create area-range when the router I'm trying to redistribute at is
not an ABR? I only have area-1 and IGRP on this router.
Creating statics is also prohibited in the lab. Right?
Thanks again
Tarek
-----Original Message-----
From: Muhamamd Durrani [mailto:dan_schaw@yahoo.com]
Sent: Tuesday, April 16, 2002 8:56 AM
To: Tarek Sabry
Cc: ccielab@groupstudy.com
Subject: Re: OSPF - IGRP
Hi Tarek ,
With Summary-Address you cannot re-distribute to other
routing protocol . Its for the Summary Address for
Ecternal Routes .
I would rather say create a Summary Address with "Area
range " commad on the router you want to summarized
the addresses on, with the mask configured on the
interfaces running IGRP. If the mask is now same as
configured on IGRP interfaces than you wil not see the
route on IGRP router .
Another way that I could see is to create a static
route on ASBR to NULL 0 and redistribute static into
IGRP process ..but again the mask SHOULD match with
interaces configured with IGRP .
Let me know id I am wrong .
Regards,
Muhammad
--- Tarek Sabry <tsabry@houston.sns.slb.com> wrote:
> Hi
>
> I understand that there may be more than one way to
> redistribute VLSM into
> FLSM. However the only way that seems to work for me
> when redistributing
> OSPF into IGRP is the brilliant method suggested by
> someone a little while
> back, whereby I need to create an intermediate OSPF
> process. I don't feel
> comfortable with just this way though, because the
> proctors may object to
> it.
>
> So let's say we have a /26 network connected to the
> OSPF side of the
> redistributing router. Someone had suggested before
> that a good way of
> achieveing what I want would be to redistribute
> connected into OSPF and
> create a "summary-address" of a /24, and this route
> would be redistributed
> into IGRP with the rest of the OSPF routes.
>
> Is that supposed to work??? Well doesn't the
> "summary-address" inject a
> route INTO OSPF and not OUT OF it?? Also how come I
> do not see any routes to
> "Null 0" after I create my OSPF summary address?
>
> What are common gotchas for OSPF summaries??
>
> Thanks a lot
> Tarek
>
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