From: Russell Lusignan (rlusignan@xxxxxxxxxxxxxxx)
Date: Mon Apr 30 2001 - 00:16:15 GMT-3
Mas,
This one is worrying me quite a bit to.. I have done quite a bit of fooling
around since I got it working.. Here is some of the stuff I have figured
out. Feel free to make comments on it (everyone):
- The summary-address command wasn't giving me null0 routes in the ospf
routing table until I did a "redistribute.. " command in the ospf process.
So basically, unless I did mutual redistribution between ospf/igrp, the
summary-address trick of getting routes into IGRP didn't work.
- It appeard that only directly connected subnets summarized by the
summary-address command on the ASBR were being redistributed successfully
into IGRP, again only if mutual redist was configured.
- So, mutual redistribute, what would happen if I did mutual redistribution
between a separate OSPF process and IGRP? I added another ospf process, here
is the basic config:
route ospf 100
router-id 170.12.1.1
area 0 authentication message-digest
network 170.10.1.0 0.0.0.255 area 0
network 170.10.12.0 0.0.0.15 area 0
!
router ospf 200
summary-address 170.10.24.0 255.255.255.128
summary-address 170.10.12.0 255.255.255.128
summary-address 170.10.13.0 255.255.255.128
summary-address 170.10.16.0 255.255.255.128
summary-address 170.10.17.0 255.255.255.128
summary-address 170.10.18.0 255.255.255.128
summary-address 170.10.19.0 255.255.255.128
summary-address 170.10.24.128 255.255.255.128
redist ospf 100 subnets
passive-interface ethernet0
passive-interface serial0
!
router igrp 50
redistribute ospf 200
network 170.10.0.0
default-metric 10000 1000 255 1 1500
The idea behind this config is to redistribute routes learned through OSPF
100 into OSPF 200. OSPF 200 summarizes all of the routes to /25 which is
the mask used on the IGRP interfaces. Now, from everything I have read in
the list and on Cisco's site and talked about with others, the
summary-addresses should summarize all of the routes learned from OSPF 100
into /25 which should then redistribute succesfully into IGRP. Only 4 of
the routes summarized appeared in IGRP, so I figured that it must be a
metric/metric-type thing.. maybe that only inter-area routes were being
successfully redistributed into IGRP, so I checked the summary-address table
on ospf process 200.. Here is what it looked like:
R1#sh ip ospf 200 summary-address
OSPF Process 200, Summary-address
170.10.24.0/255.255.255.128 Metric 138, Type 2, Tag 0
170.10.12.0/255.255.255.128 Metric 20, Type 2, Tag 0
170.10.13.0/255.255.255.128 Metric 16777215, Type 0, Tag 0
170.10.16.0/255.255.255.128 Metric 148, Type 2, Tag 0
170.10.17.0/255.255.255.128 Metric 148, Type 2, Tag 0
170.10.18.0/255.255.255.128 Metric 148, Type 2, Tag 0
170.10.19.0/255.255.255.128 Metric 148, Type 2, Tag 0
170.10.24.128/255.255.255.128 Metric 129, Type 2, Tag 0
The freaky thing is that only 170.10.24.0/25, 170.10.24.128/25, and
170.10.12.0/25 appeared in the IGRP routing table on R8. I can't figure out
what the common thing is with only those routes.
I have tried this many ways.. not once have I felt comfortable that this
will work if I do it from scratch, or if I reboot the router. So basically
if I get this sort of problem in my lab (which I probably will), I will
cross my fingers and hope it works.
There is no technical explanation that I can find or make that explains the
behaviour of IGRP. And the kicker is, if I just add null0 routes on the
ASBR with a /25 mask it redistributes no problem. I hate IGRP.
-Russ
> -----Original Message-----
> From: Mas Kato [mailto:tealp729@home.com]
> Sent: Sunday, April 29, 2001 9:07 PM
> To: 'Russell Lusignan'; ccielab@groupstudy.com
> Subject: RE: OSPF summar-address into IGRP
>
>
> Russ,
>
> Allow me to kick the corpse a little... I have not been able
> to get this
> scenario to work, at least with 12.x. I could never get a
> null0 route to
> install on its own when the summary's major network was the same as my
> OSPF network and where its mask matched my interface leading out of
> OSPF. 'show ip ospf summary' would show the summary with a very high
> metric--apparently unreachable.
>
> I'm sure your research has revealed that the documentation doesn't
> support this scenario and that the, uh, "official" way to do
> this is to
> either install a static summary route to null0 or source a default
> route.
>
> I'm so concerned with the possibility of having to defend situations
> like this during the lab exam, I recently wrote to the CCIE program
> about it. I asked point blank whether we could be asked to exploit
> undocumented "features" of IOS behavior. We all know how porous the
> documentation is--we'll see...
>
> So how on Earth did you finally get it to work? Does it
> survive reboots
> and such?
>
> Regards,
>
> Mas Kato
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Russell Lusignan
> Sent: Sunday, April 29, 2001 3:48 PM
> To: 'ccielab@groupstudy.com'
> Subject: RE: OSPF summar-address into IGRP
>
>
> Ummm... I spent a few days trying to figure this one out to no avail,
> as
> soon as I post to this list my problem, it works. So, by adding the
> "summary-address 170.10.12.0 255.255.255.128" to R1, that subnet now
> shows
> up on R8. Weird. So for anyone reading my previous post about this
> problem, don't worry about it :)
>
> Too bad we don't have the ability to post to this list while doing the
> actual lab :)
>
> sorry
> -Russ
>
>
>
> > -----Original Message-----
> > From: Russell Lusignan [mailto:rlusignan@birdonawire.com]
> > Sent: Sunday, April 29, 2001 5:08 PM
> > To: 'ccielab@groupstudy.com'
> > Subject: OSPF summar-address into IGRP
> >
> >
> > Hey group,
> >
> > This topic has been beaten to death, but I haven't be able to
> > find anything
> > in the archives on what is happening.
> >
> > OSPF IGRP
> > ------------------R1-------------------R8
> > 170.10.12.0/28 170.10.20.0/25
> >
> > I want the /28 to redistribute into IGRP, I know R1 won't
> advertise it
> > because it's not a /25. I have ready many posts about
> people using a
> > summary-address on R1 to summarize the /28 into a /25. This
> > does not work
> > for me. On R1, if I do "summary-address 170.10.12.0
> 255.255.255.128"
> > shouldn't that be enough to get that /28 into IGRP as a /25?
> > This works if
> > I place a null0 route on R1 with a /25 manually, and I have
> > managed to get a
> > default-network to R8, but if these are not permitted on the
> > lab, I am not
> > sure how else to do it.
> >
> > I recall reading a post a while back where someone mentioned
> > that when you
> > create a summary-address in ospf it should automatically
> > create a null0
> > route to that subnet, I know EIGRP does this, but wasn't
> > aware that ospf did
> > it. When I do create a summary-address there is no null0
> > route created with
> > OSPF...
> >
> > -Russ
> > **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
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:30:01 GMT-3