From: Richardson, Cheryl (cheryl.richardson@xxxxxxxx)
Date: Sun Dec 12 1999 - 21:55:35 GMT-3
Right after my last note, I tried a "just to see" reboot and then "summary
address" out of desperation. And
even though it was against everything I have read and was taught, it worked.
I took Caslow's ECP1 course back a few months ago and we studied the OSPF to
IGRP topic. I learned
four things:
1) "area range" went on ABRs to summarize within OSPF between areas
2) "summary address" went on ASBR to summarize routes from other protocols
upon
redistribution INTO OSPF.
3) The only other way to fix the VLSM issue was to use "ip default-network".
4) If "summary address" worked on a redistribution FROM OSPF into another
protocol, it was a fluke.
Caslow's BRS book example actually shows redistributing from IGRP into OSPF.
And, the Cisco documentation
explicitely states about the "summary address" command..
"For OSPF, this command summarizes only routes from other routing protocols
that are being redistributed
into OSPF"
Obviously, #4 worked for me. So, during the exam, I suppose you should just
go for the one that seems to
work? I still have doubts. Anyone care to comment?
Also, I do not have the Little Black book that was referenced. Could you
provide a quote regarding the subject?
Thanks --
> -----Original Message-----
> From: pkm@calweb.com [SMTP:pkm@calweb.com]
> Sent: Sunday, December 12, 1999 4:55 PM
> To: Richardson, Cheryl
> Subject: Re: [sc] Classic FLSM -> VLSM issue
>
> No problem. Use on the OSPF ASBR router, the command summary-address. This
> will
> summarize your vlsm to whatever subnet mask you are using inside your IGRP
> domain. The other command area range is a good command but does not apply
> to
> this kind of scenario. By the way, avoid routing loops by using a
> distribute-list command in the ospf routing domain.
>
> Reference used: Calsow book and specifically Cisco Routers for IP Routing
> (Little Black Book) by Innokenty Rudenko, CCIE page 340-341. Here is the
> config:
>
> interface loopback0
> ip add 10.10.0.2 255.255.255.255.255
>
> int ethernet0
> ip add 10.10.2.1 255.255.255.
>
> int serial 0
> ip add 10.204.0.1 255.255.10 255.255.255.252
>
> router ospf 10
> summary-address 10.10.0.0 255.255.0.0
> redistribute igrp 10 metric 10 subnets
> network 10.10.0.0 0.0.0255.255 area 10
> distribute-list 10 out igrp 10
>
> router igrp 10
> redistribute ospf 10 metric 10000 1 255 1 1500
> pass-int ethernet0
> pass-int loopback0
> pass-int serial1
> network 10.0.0.0
>
> ip classless
>
> access-list 10 deny 10.10.0.0 0.0.255.255
> access-list 10 permy any
>
> Here is another good link for RIP and OSPF redist.
>
> Have fun.
>
> Phillip Moulay
> Future CCIE (Lab. in Dec. 16 an Dec. 17)
>
> "Richardson, Cheryl" wrote:
>
> > I know it is hard to see without seeing the configs. Actually, "ip
> > classless" is one of the first things
> > I configure, in addition to "no ip domain-lookup", etc. Everything
> works
> > fine with a default route and
> > subnets that are not in my routing table but part of the class of
> network
> > that I know of still take the
> > default route. (normal "ip classless" behavior). But, when I configure
> an
> > aggregate address under
> > BGP, I end up with a supernet route to null0. Now subnets that are not
> in
> > my routing table but
> > part of the supernet route go to null0. I consider this normal
> behavior,
> > just the wrong approach on
> > my part.
> >
> > This is what makes me think that I should have taken the area-range
> > approach. But I still can't
> > get VLSM routes to summarize within the backbone area 0.
> >
> > I also tried Brian's approach of placing the area range commands on each
> > router within area 0
> > (even though I thought the command only applied to the ABRs) and it
> still
> > didn't work for me.
> > Has anyone actually seen this work, and possibly have working configs?
> >
> > Thanks --
> > Cheryl Richardson
> >
> > > -----Original Message-----
> > > From: Mark Adams [SMTP:adamsmw@earthlink.net]
> > > Sent: Sunday, December 12, 1999 1:37 PM
> > > To: Richardson, Cheryl
> > > Subject: Re: [sc] Classic FLSM -> VLSM issue
> > >
> > > Now, my route table has a supernet and sends all pings for the
> > > "unknown" VLSM subnets to the bit bucket (instead of taking my default
> > > route). This would imply that I made the wrong choice.
> > >
> > > I'm not an expert at this, but this sounds like a side effect of a <no
> IP
> > > Classless> configuration. The default setting of IP Classless depends
> on
> > > IOS version, so I'd start here.
> > >
> > >
> > > "Richardson, Cheryl" wrote:
> > >
> > > Has anyone run into the following:
> > >
> > > OSPF with VLSM subnets with mutual redistribution to IGRP. How
> do
> > > you get
> > > the IGRP router to
> > > recognize the VLSM subnets?
> > >
> > > My thoughts were that there were two choices:
> > > 1) Either "area range" the VLSM nets so that they are /24 when
> they
> > > hit
> > > IGRP.. or
> > > 2) Do the "ip default-network" thing
> > >
> > > Since I had /28 subnets in area 0 (which is where the redist
> occurs)
> > > and did
> > > not feel that area 0 routes could be
> > > summarized and effect IGRP (I know that the summaries could
> apply to
> > > the
> > > other areas), I chose "ip default-network".
> > >
> > > Great, everyone can ping everyone. Then along comes BGP on the
> IGRP
> > > router
> > > and I am asked to create
> > > a supernet for all the routes to send to the EBGP router. Now,
> my
> > > route
> > > table has a supernet and sends all pings
> > > for the "unknown" VLSM subnets to the bit bucket (instead of
> taking
> > > my
> > > default route). This would imply that
> > > I made the wrong choice. But, how can you summarize within area
> 0?
> > > summary-address applies to redistribution
> > > from the outside protocol into OSPF. Is there another choice
> that I
> > > am
> > > missing?
> > >
> > > Thanks for any help!
> > > Cheryl Richardson
> > >
> > > --
> > > To unsubscribe: echo unsubscribe cisco-cert | mail
> > > majordomo@cciecert.com
> > >
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