From: smaljure@xxxxxxxxxxxxxxxxx
Date: Tue Sep 26 2000 - 10:24:28 GMT-3
Very counter-intuitive but surely works...
Thanks for the explanation Tony/Kevin
Sanjay
-----Original Message-----
From: Tony Olzak [mailto:aolzak@buckeye-express.com]
Sent: Monday, September 25, 2000 5:28 PM
To: smaljure@cibernetworks.com; kbaumgar@cisco.com
Cc: ccielab@groupstudy.com
Subject: Re: Redistributing OSPF to IGRP
The summary-address command is used in OSPF in this scenario, but it isn't
for its benefit. It's only to create a route that has the same mask as the
IGRP enabled interface so that it will receive routes from OSPF with
variable subnets.
R1----R2----R3
/26
R1 has network 172.17.59.128/26 and is only running IGRP.
R2 has networks 172.17.59.0/29, 172.17.59.16/28, 172.17.59.32/27, and
172.17.59.128/26
On R2 you will use this in OSPF command:
summary-address 172.17.59.0 255.255.255.192
This creates a route on R2 that says 172.17.59.0/26 (note it has the same
mask as the IGRP router) with next hop Null0. This route will redistribute
into IGRP because it has the same mask and R1 will get a route that says
172.17.59.0/26 (which contains all the previous networks except
172.17.59.128/26) with next hop R2. When R1 sends a packet destined for one
of those networks off of R2, the routing table on R2 (with more specific
routes to each network) will route it to the proper destination.
Tony
----- Original Message -----
From: <smaljure@cibernetworks.com>
To: <aolzak@buckeye-express.com>; <kbaumgar@cisco.com>
Cc: <ccielab@groupstudy.com>
Sent: Monday, September 25, 2000 4:00 PM
Subject: RE: Redistributing OSPF to IGRP
> Hi
> I also received Kevin's reply on this one...
> Let us see if I stated myself correctly. I am going to generalize the
> situation a little to see if we can arrive at a conclusion.
>
> R1------R2-----R3
> /26
>
> R1 is running only IGRP.
> Link between R1 and R2 is a /26
> R2 is the ASBR running IGRP and OSPF (Redistribution is happening on this
> box)
> R3 is running only OSPF
>
> Let us say R1 has 5 routes in its table
>
> 172.16.1.32/24
> 172.16.2.32/24
> 172.16.3.32/24
> 172.16.4.64/26
> 172.16.5.64/26
>
> When IGRP makes the IGRP update to R2, only two of the above will survive
> because of IGRP/Classful limitations.... those would be 172.16.4.64/26 and
> 172.16.5.64/26
>
> Now when we redistribute these routes in to OSPF on R2, I would use the
> summary-address 172.16.0.0 255.255.0.0 within the OSPF process...and hence
> R3 should receive the 172.16.0.0/16 route.
>
> My question is
>
> Why should OSPF care how we are summarizing external routes? Isn't the
> "mask" used with the "summary address.." command supposed to be at the
> discretion of the administrator?
>
> Of course I could be wrong here, would be great if u guys can clarify.
>
> Thanks for your time
>
> Sanjay
>
>
>
>
>
> -----Original Message-----
> From: Tony Olzak [mailto:aolzak@buckeye-express.com]
> Sent: Monday, September 25, 2000 3:15 PM
> To: Maljure, Sanjay; 'Kevin Baumgartner'
> Cc: ccielab@groupstudy.com
> Subject: Re: Redistributing OSPF to IGRP
>
>
> It's not incidental. If you use the "summary-address" command and specify
> the mask as /16, but the same network is /26 on the IGRP router, your
> network will not redistribute.
>
>
> ----- Original Message -----
> From: "Maljure, Sanjay" <smaljure@cibernetworks.com>
> To: "'Kevin Baumgartner'" <kbaumgar@cisco.com>; "Tony Olzak"
> <aolzak@buckeye-express.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Monday, September 25, 2000 1:34 PM
> Subject: RE: Redistributing OSPF to IGRP
>
>
> > Hi Everyone,
> > I was just going through this interesting thread and I want to sound u
> guys
> > off on what I think...just to confirm if I am right or wrong
> >
> > So when we redistribute from OSPF in to IGRP, only the subnets that
match
> > the mask on the link in the IGRP domain, will make it to an IGRP router.
> > This is irrespective of whether we are using the "summary address...."
> > command when redistributing IGRP in to OSPF. I think it is just
incidental
> > that the mask used with the "summary address.." command and the mask on
> the
> > link connecting to the IGRP world are the same.
> >
> > Is this correct...Please confirm
> > Thanks
> > Sanjay
> >
> > -----Original Message-----
> > From: Kevin Baumgartner [mailto:kbaumgar@cisco.com]
> > Sent: Monday, September 25, 2000 12:44 PM
> > To: Tony Olzak
> > Cc: ccielab@groupstudy.com
> > Subject: Re: Redistributing OSPF to IGRP
> >
> >
> > I tried your setup and used the network that was sent to R2 as
> > the default-network. It didn't work. Not really suprised as this
> > is not a classful network.
> >
> > But your solution of how to redistribute non-classful (subnetted)
> > routes into IGRP is very good.
> >
> > Kevin
> >
> >
> >
> > At 12:05 PM 9/25/00 -0400, you wrote:
> > >Kevin,
> > >
> > >Default-network will work also, some scenarios just don't allow that
> > >command. I figured we better find out how to do it without using static
> > >routes or the default-network command.
> > >
> > >Tony
> > >
> > >----- Original Message -----
> > >From: "Kevin Baumgartner" <kbaumgar@cisco.com>
> > >To: <aolzak@buckeye-express.com>
> > >Cc: <ccielab@groupstudy.com>
> > >Sent: Monday, September 25, 2000 12:09 AM
> > >Subject: Re: Redistributing OSPF to IGRP
> > >
> > >
> > > > Good catch, I didn't know it would work this way.
> > > >
> > > > What about using this as a default-network on R2?
> > > >
> > > > Kevin
> > > >
> > > > >
> > > > > This is a multi-part message in MIME format.
> > > > >
> > > > > ------=_NextPart_000_01B5_01C02682.08DEFF90
> > > > > Content-Type: text/plain;
> > > > > charset="iso-8859-1"
> > > > > Content-Transfer-Encoding: quoted-printable
> > > > >
> > > > > All,
> > > > >
> > > > > Just wanted to close this topic and share my findings.
> > > > >
> > > > > Without using the default-network command or static routes, the
only
> > way
> > >=
> > > > > to redistribute OSPF into IGRP with VLSM is to use the
> summary-address
> > =
> > > > > command on the OSPF router. This route will be redistirbuted into
> IGRP
> > =
> > > > > and allow that router to communicate with the other networks. One
> > catch
> > >=
> > > > > is that this summary address must have the same mask as the IGRP
> link
> > =
> > > > > that is enabled on that major network. Example:
> > > > >
> > > > > Router 1
> > > > > !
> > > > > interface Loopback1
> > > > > ip address 172.17.59.1 255.255.255.248
> > > > > !
> > > > > interface Loopback2
> > > > > ip address 172.17.59.17 255.255.255.240
> > > > > !
> > > > > interface Loopback3
> > > > > ip address 172.17.59.33 255.255.255.224
> > > > > !
> > > > > interface Serial1
> > > > > ip address 172.17.59.129 255.255.255.192
> > > > > !
> > > > > router ospf 100
> > > > > summary-address 172.17.59.0 255.255.255.192
> > > > > redistribute igrp 100 metric 64 subnets
> > > > > passive-interface Serial1
> > > > > network 172.17.59.0 0.0.0.7 area 0
> > > > > network 172.17.59.16 0.0.0.15 area 1
> > > > > network 172.17.59.32 0.0.0.31 area 2
> > > > > !
> > > > > router igrp 100
> > > > > redistribute ospf 100 metric 64 10 255 1 1500
> > > > > passive-interface Loopback1
> > > > > passive-interface Loopback2
> > > > > passive-interface Loopback3
> > > > > network 172.17.0.0
> > > > > !
> > > > > ip classless
> > > > >
> > > > >
> > > > > Router 2
> > > > > !
> > > > > interface Ethernet0
> > > > > ip address 10.0.0.1 255.0.0.0
> > > > > !
> > > > > interface Serial0
> > > > > ip address 172.17.59.130 255.255.255.192
> > > > > clockrate 64000
> > > > > !
> > > > > router igrp 100
> > > > > network 10.0.0.0
> > > > > network 172.17.0.0
> > > > > !
> > > > > ip classless
> > > > >
> > > > > Router 1 and 2 are connected through their serial interfaces. The
> mask
> > =
> > > > > on this connection is /26, so the summary on Router 1 must have a
> mask
> > =
> > > > > of /26 also or it will not redistribute to router 2. At first I
> tried
> > a
> > >=
> > > > > summary of 172.17.0.0 255.255.0.0 thinking that since IGRP only =
> > > > > understood classful networks that the summary address would have
to
> be
> > a
> > >=
> > > > > class B standard mask. The route did not make it to Router 2.
After
> =
> > > > > skimming through Doyle's book, it reminded me how since the
> 172.17.0.0
> > =
> > > > > network on router 2 had a mask of /26, only matching subnet masks
> > would
> > >=
> > > > > redistribute from router 1.
> > > > >
> > > > > Tony
> > > > >
> > > > >
> > > > > ------=_NextPart_000_01B5_01C02682.08DEFF90
> > > > > Content-Type: text/html;
> > > > > charset="iso-8859-1"
> > > > > Content-Transfer-Encoding: quoted-printable
> > > > >
> > > > > <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
> > > > > <HTML><HEAD>
> > > > > <META content=3D"text/html; charset=3Diso-8859-1" =
> > > > > http-equiv=3DContent-Type>
> > > > > <META content=3D"MSHTML 5.00.3018.900" name=3DGENERATOR>
> > > > > <STYLE></STYLE>
> > > > > </HEAD>
> > > > > <BODY bgColor=3D#ffffff>
> > > > > <DIV><FONT face=3DArial size=3D2>All,</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Just wanted to close this topic
and
> =
> > > > > share my=20
> > > > > findings.</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Without using the default-network
=
> > > > > command or static=20
> > > > > routes, the only way to redistribute OSPF into IGRP with VLSM is
to
> > use
> > >=
> > > > > the=20
> > > > > summary-address command on the OSPF router. This route will be =
> > > > > redistirbuted=20
> > > > > into IGRP and allow that router to communicate with the other
> > networks.
> > >=
> > > > > One=20
> > > > > catch is that this summary address must have the same mask as the
> IGRP
> > =
> > > > > link that=20
> > > > > is enabled on that major network. Example:</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Router 1</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>interface Loopback1<BR> ip
> > address
> > >=
> > > > > 172.17.59.1=20
> > > > > 255.255.255.248<BR>!<BR>interface Loopback2<BR> ip address =
> > > > > 172.17.59.17=20
> > > > > 255.255.255.240<BR>!<BR>interface Loopback3<BR> ip address =
> > > > > 172.17.59.33=20
> > > > > 255.255.255.224<BR>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>interface Serial1<BR> ip
> address
> > =
> > > > > 172.17.59.129=20
> > > > > 255.255.255.192</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>router ospf =
> > > > > 100<BR> summary-address=20
> > > > > 172.17.59.0 255.255.255.192<BR> redistribute igrp 100 metric
> > 64=20
> > > > > subnets<BR> passive-interface Serial1<BR> network
> > 172.17.59.0
> > >=
> > > > > 0.0.0.7=20
> > > > > area 0<BR> network 172.17.59.16 0.0.0.15 area
> > 1<BR> network=20
> > > > > 172.17.59.32 0.0.0.31 area 2</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>router igrp
> 100<BR> redistribute
> > =
> > > > > ospf 100=20
> > > > > metric 64 10 255 1 1500<BR> passive-interface=20
> > > > > Loopback1<BR> passive-interface =
> > > > > Loopback2<BR> passive-interface=20
> > > > > Loopback3<BR> network 172.17.0.0<BR>!<BR>ip
> > classless</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Router 2</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>interface Ethernet0<BR> ip
> > address
> > >=
> > > > > 10.0.0.1=20
> > > > > 255.0.0.0<BR> !<BR>interface Serial0<BR> ip address =
> > > > > 172.17.59.130=20
> > > > > 255.255.255.192<BR> clockrate 64000</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>!</FONT></DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>router igrp
100<BR> network=20
> > > > > 10.0.0.0<BR> network 172.17.0.0<BR>!<BR>ip
> classless</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Router 1 and 2 are connected
> through
> > =
> > > > > their serial=20
> > > > > interfaces. The mask on this connection is /26, so the summary on
> > Router
> > >=
> > > > > 1 must=20
> > > > > have a mask of /26 also or it will not redistribute to router 2.
At
> =
> > > > > first I=20
> > > > > tried a summary of 172.17.0.0 255.255.0.0 thinking that since IGRP
> > >only=20
> > > > > understood classful networks that the summary address would have
to
> be
> > a
> > >=
> > > > > class B=20
> > > > > standard mask. The route did not make it to Router 2. After
skimming
> =
> > > > > through=20
> > > > > Doyle's book, it reminded me how since the 172.17.0.0 network on
> > router
> > >=
> > > > > 2 had a=20
> > > > > mask of /26, only matching subnet masks would redistribute from
> > >router=20
> > > > > 1.</FONT></DIV>
> > > > > <DIV> </DIV>
> > > > > <DIV><FONT face=3DArial size=3D2>Tony</FONT></DIV>
> > > > > <DIV> </DIV></BODY></HTML>
> > > > >
> > > > > ------=_NextPart_000_01B5_01C02682.08DEFF90--
> > > > >
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