From: Sandro Ciffali (sandyccie@xxxxxxxxx)
Date: Wed May 23 2001 - 18:44:52 GMT-3
Daniel,
There was one more idea braught up in the discussion which redistributes /28
to /24 without introducing E2 route, that was to create another loop back
interface with a subnet of same major network as /28 (for example if you had
133.4.10.16/28 as backbone, then create a loopback 133.4.10.32/28 on one of
the nonasbr spoke) keep this loopback on an entire different area and
summarize this area into the backbone as a /24, So backbone will have a /24
IO route and /28 connected route, /24 will get redistributed in igrp.
Sandro
----- Original Message -----
From: "YOUNG, DANIEL (SBCSI)" <dy3519@sbc.com>
To: "Sandro Ciffali" <sandyccie@yahoo.com>; "Devender Singh"
<devender.singh@cmc.cwo.net.au>; "Mohamed Heeba" <MAHeeba@itqan.co.ae>;
<ccielab@groupstudy.com>
Sent: Wednesday, May 23, 2001 4:47 PM
Subject: RE: OSPF summary and redistribution
>
> I believe that the "correct" way is per Cisco documentation:
> http://www.cisco.com/warp/customer/105/52.html
>
> Add a static route in the OSPF ASBR that points to the OSPF domain with a
> /24 mask, but with a next hop of null0. Then, redistribute static routes
> into RIP. This allows the OSPF addressed to be advertised to the RIP
domain.
> The ASBR Router would still have more specific routes learned from OSPF in
> its routing table, so the best routing decisions will be made. This
prevents
> black holes.
>
> The summary-address solution is another way, but it is inefficient as it
> creates addtional entries on the link-state database. Summary-addresses
are,
> per Devender, supposed to be used to summarize external routes (type 5
LSAs)
> -- not the other way around. However, if you are prohibited from creating
> static routes, then this is your only other viable option.
>
> Can I get yeas or nays on this?
>
> Daniel
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Sandro Ciffali
> Sent: Tuesday, May 22, 2001 4:39 PM
> To: Devender Singh; Mohamed Heeba; ccielab@groupstudy.com
> Subject: Re: OSPF summary and redistribution
>
>
> Devender,
> I agree with you completly on this, This is the way i plan to distribute
/28
> to /24 on asbr from ospf to rip or igrp, But i have heard through couple
of
> guys that it is makred as modifying ospf database hence lost points, I
> seriously hope someone would tell us the correct way of doing this.
>
> Sandro
> ----- Original Message -----
> From: "Devender Singh" <devender.singh@cmc.cwo.net.au>
> To: "Mohamed Heeba" <MAHeeba@itqan.co.ae>; <ccielab@groupstudy.com>
> Sent: Tuesday, May 22, 2001 7:02 PM
> Subject: RE: OSPF summary and redistribution
>
>
> > Hai Mohammad,
> > Sorry to come the subject a bit late.
> >
> > I agree this is Scary and I agree with what ever you said. What if this
> > situation
> > arises in the lab :-(((. I wish to discuss this bit futher.
> >
> > This my understanding:
> >
> > Normally summary-address used create a summary from type 5 LSA on ASBR
> (Say
> > rip to ospf ). But what happens when we use it to summarise the other
way
> > around. When we redistribute ospf into say RIP, by rules it will get
> > redistributed into RIP, but if the mask on the outgoing RIP interface
> does
> > not match routes will not be progated into rip. The mask on the outgoing
> > interface does not have anything to do with basic process of
> redistribution.
> > Now if we redistribute RIP back into ospf without any route-map or
> > distribute-lists all this route will be inserted back into ospf but they
> > will not bother ospf because internal routes have preference over
external
> > routes. Now the summary command ( our hack) does its job and pushes it
> back
> > to RIP with the mask we want also into ospf domain as external. Rest
> > everything is normal.
> >
> > Does this make sense to you.
> >
> > Best regards
> >
> > Devender Singh
> > BE(Hons), CCNP
> > IP Solution Specialist
> >
> >
> > -----Original Message-----
> > From: Mohamed Heeba [mailto:MAHeeba@itqan.co.ae]
> > Sent: Saturday, 12 May 2001 9:04
> > To: 'ccielab@groupstudy.com'
> > Subject: OSPF summary and redistribution
> >
> >
> > guys ;
> > i have reached a conculation about the problem of the OSPF and
> summarization
> > /redistribution and wanted to share it with you who are interested .
> > i have revised Doyles chapter of redistribution ,there is an example of
> > redistributing RIP into IS-IS and at the end of this chapter ,(RIP is
/24
> > and ISIS is /24 and /28 )
> > CLEARLY ,he NEVER use the command summary-address to summarize the ISIS
> > routes to the RIP and clearly also mentioned that ISIS /28 routes should
> be
> > summarized to RIP by using STATIC ROUTES !!!!.
> > so the point is the summary command should only be used to summarize
> > extrenal routes INTO ISIS or OSPF .but our problem is that we were
trying
> to
> > go around this problem to avoid the use of static routes ,while in fact
it
> > is an easy way to solve this problem.
> > going around the problem can may be done by a command like ip
> > default-network ,but this will require the major class network to be
> > different in both domains.
> > well...i guess in the real lab there should be way to avoid using the
> > summary address in opposite way and create more problems ....or they may
> > allow to use just single static route somewhere :))))))
> >
> >
> > hope someone can comment on this
> > Mohamed
> > **Please read:http://www.groupstudy.com/list/posting.html
> > **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
**Please read:http://www.groupstudy.com/list/posting.html
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