From: Mas Kato (tealp729@xxxxxxxx)
Date: Mon Apr 30 2001 - 04:00:19 GMT-3
Russ,
Thanks, I took it for granted that mutual redistribution was part of the
deal. What's got me in stitches after reading about your findings is
I -couldn't- get it to work with my directly connected OSPF subnet.
All my summary would ever look like is this one from your OSPF process
200:
170.10.13.0/255.255.255.128 Metric 16777215, Type 0, Tag 0
...with that peculiar metric; The only difference being I was trying to
summarize a directly-connected OSPF /28 route into an IGRP /24 AS. 'show
ip protocols' would indicate that address summarization was taking place
in my OSPF process, but the field that would indicate "for which
networks" would be blank.
The only way I ever got the OSPF 'summary-address' command to work was
by employing it exactly as it is documented. I redistributed a /30 from
an EIGRP AS on the other side of the network. One philosophy, I'm told,
is to preserve the specificity of the route as long as possible, so I
tried to summarize the route at the OSPF/IGRP ASBR. Nope. I had to place
the command exactly where the docs say to place it--at the ASBR
redistributing the route in.
I've long since moved on to other topics, uneasily writing this one off
as bug that may be exploited perhaps in earlier or different builds of
the IOS (I'm running 12.1(7)). I'm just going to have to find a way to
work-around it and defend my tactics if I get dealt a situation that
calls for it in the lab. My uneasiness has only grown after wrestling
with glitches in other areas as well--like the whole DDR mess,
NLSP-to-IPX EIGRP aggregate route redistribution, DLSW filtering logic,
etc.--because of things like this, I'm grateful this group exists!!
Mas
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Russell Lusignan
Sent: Sunday, April 29, 2001 8:16 PM
To: 'ccielab@groupstudy.com'
Subject: RE: OSPF summar-address into IGRP
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
**Please read:http://www.groupstudy.com/list/posting.html
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