From: Kevin Baumgartner (kbaumgar@xxxxxxxxx)
Date: Thu Sep 21 2000 - 14:44:46 GMT-3
This is not a split-horizon issue. OSPF doesn't have a problem with split-horiz
on.
The issue is that when you do a redistribute IGRP (or any routing protocol) int
o OSPF, external
LSA's will now be send out periodically from R1 and in this example the ISDN in
terface. This
means that ISDN will always be up. So really defeating the purpose of using "ip
ospf demand
circuit" on the ISDN interfaces.
So how to prevent this from happening. Create a filter that deny LSA type 5 u
pdates to be
sent to 172.17.2.253 255.255.255.255 (or 172.17.2.240 network), the BRI neighb
or interface
on R2.
The igrp network of 172.17.0.0 is to a neighbor router that I don't show in t
his picture.
It's on a different interface on R1 that I don't show in the picture. I don't w
ant IGRP updates
to be send on any other interfaces.
Kevin
At 01:04 PM 9/21/00 -0400, you wrote:
>forgive me if I missed something, but it appears that this is a route-feedback
problem and what
>you are doing is not allowing the "re-distribution" of the 172.17.2.240 networ
k back into OSPF from
>IGRP. But why is this not stopped by split-horizon anyways? Also where is the
interface with network
>20 that you are routing igrp? And why are you running igrp on network 172.17.0
.0 if you made
>all the interfaces passive?
>
>Just trying to understand why this works at all - I guess I'll have to go to t
he lab and hook it up.
>
>Julie Ann
>
>
>At 09:03 AM 9/21/2000 -0700, Kevin Baumgartner wrote:
>>I think I have solved the problem. I have set my routers to be as close
>>as possible to what you where doing.
>>
>>IGRP
>> \ AREA 2 AREA 3
>> R1----s0/0----------------------------- s0/0 ---- R2---e0/0 ------- e
0/0 ---- R4
>> A | | |
>> R | | AREA 2 |
>> E | -----BRI2/0 ------------------------ BRI1/0 --
>> A |
>> 0 |
>> R3
>>
>>So the first thing I tried was defining the OSPF virtual-link on R1 and R2 fo
r Area3
>>with OSPF demand circuit. It worked as expected. The ISDN line would come up
>>once to do a topology update and then the line would go down and stay down.
>>
>> The next step was to try redistributing IGRP into OSPF on R1. This caused
the
>>line to always stay up. As soon as the dialer timeout expired it would call a
gain.
>>
>> So I did some debugging to see what was happening
>>
>>debug dialer
>>debug ip ospf lsa-generation
>>
>>And I saw a message of "Generating external LSA for 172.17.2.253 255.255.255.
255 Type 5"
>>
>>So I created a route-map that deny any redistribution of the 172.17.2.240 (IS
DN Network) into OSPF.
>>Worked like a charm. The ISDN link stayed down and only came up when I took t
he Serial link down.
>>Still a little fussy what happening here with redistribution and OSPF demand
circuits but my theory
>>is that OSPF demand circuits only suppress internal LSA's not external LSA's.
Hence the need for
>>this route filter as redistributing other routing protocols into OSPF is goin
g to generate external LSA
>>updates.
>>
>> Configurations
>>
>> R1
>>
>> interface Ethernet0/0
>> ip address 172.17.1.3 255.255.255.240
>>!
>>interface Serial0/0
>> bandwidth 2000
>> ip address 172.17.2.1 255.255.255.240
>> clockrate 2000000
>>!
>>interface BRI2/0
>> bandwidth 56
>> ip address 172.17.2.254 255.255.255.240
>> encapsulation ppp
>> ip ospf demand-circuit
>> dialer map ip 172.17.2.253 name R2 broadcast 87772002
>> dialer-group 1
>> isdn switch-type basic-5ess
>> ppp authentication chap
>>!
>>username R2 password cisco
>>dialer-list 1 protocol ip permit
>>!
>>router ospf 1
>> area 0 range 172.17.1.0 255.255.255.0
>> area 2 range 172.17.2.0 255.255.255.0
>> area 2 virtual-link 172.17.3.1
>> redistribute igrp 1 metric 1 subnets route-map igrp-ospf
>> passive-interface TokenRing1/0
>> network 172.17.1.3 0.0.0.0 area 0
>> network 172.17.2.1 0.0.0.0 area 2
>> network 172.17.2.254 0.0.0.0 area 2
>> network 172.17.193.1 0.0.0.0 area 0
>>!
>>access-list 1 permit 172.17.2.240 0.0.0.15
>>access-list 2 permit any
>>!
>>route-map igrp-ospf deny 10
>> match ip address 1 <<<<< Deny sending LSA external on
to ISDN.
>>!
>>route-map igrp-ospf permit 20
>> match ip address 2
>>!
>>
>>router igrp 1
>> redistribute ospf 1 metric 10000 200 255 1 1500
>> passive-interface Ethernet0/0
>> passive-interface Serial0/0
>> passive-interface BRI2/0
>> network 20.0.0.0
>> network 172.17.0.0
>>!
>>ip classless
>>
>>R2
>>----
>>
>>interface Ethernet0/0
>> ip address 172.17.3.1 255.255.255.252
>>!
>>interface Serial0/0
>> bandwidth 2000
>> ip address 172.17.2.2 255.255.255.240
>>!
>>interface BRI1/0
>> bandwidth 56
>> ip address 172.17.2.253 255.255.255.240
>> encapsulation ppp
>> ip ospf demand-circuit
>> dialer map ip 172.17.2.254 name R1 broadcast 87772001
>> dialer-group 1
>> isdn switch-type basic-5ess
>> ppp authentication chap
>>!
>>username R1 password cisco
>>dialer-list 1 protocol ip permit
>>!
>>router ospf 1
>> area 2 virtual-link 172.17.2.254
>> network 172.17.2.2 0.0.0.0 area 2
>> network 172.17.2.253 0.0.0.0 area 2
>> network 172.17.3.1 0.0.0.0 area 3
>>
>>
>>
>>
>>At 05:26 PM 9/20/00 -0700, you wrote:
>> >That's correct. It is very close to a real lab
>> >scenario according to some romours I heard.
>> >
>> >An the thing is, I had it working once. This time it
>> >doesn't work.
>> >
>> >Sam
>> >--- Daniel Keller <DMKeller@comdisco.com> wrote:
>> > > The problem is that area 2 is a virtual link.
>> > > Because of this, LS updates will always keep the
>> > > line dialing. Can you place the bri connections
>> > > into a different area? If not you will need to find
>> > > an alternative, such as using backup interface. Is
>> > > this from a lab that you have?
>> > >
>> > > Dan Keller
>> > >
>> > > >>> Sam Munzani <smunzani@yahoo.com> 09/20/00
>> > > 05:50PM >>>
>> > > Hi Group,
>> > >
>> > > I have attached my configs with e-mail. Tell me what
>> > > am I doing wrong? ISDN keeps flapping. Scenario is
>> > > as
>> > > below.
>> > >
>> > > Grumpy--(Bri 0) ------ (Bri 0 )-- Sleepy
>> > >
>> > > The BRI link is in OSPF area 2. I used OSPF demmand
>> > > circuit and also used no peer neighbor route.
>> > > Bandwidth is not specified on serial link so it will
>> > > be default T1 for frame link.
>> > >
>> > > I have also attached "ip ospf data" results on each
>> > > router. I had it working some time ago but this time
>> > > it doesn't work.
>> > >
>> > > Rather than throwing some hints please justify
>> > > proper
>> > > methodology for this configuration. I am sure
>> > > everybody will get hit by this scenario in some
>> > > flavor
>> > > so it is important.
>> > >
>> > > Sam
>> > >
>> > >
>> > > --- Daniel Keller <DMKeller@comdisco.com> wrote:
>> > > > Because the BRI's are in area 0, OSPF updates will
>> > > > constantly be triggering the ISDN line. How do
>> > > you
>> > > > keep this line from always coming up?
>> > > >
>> > > > >>> Kevin Baumgartner <kbaumgar@cisco.com>
>> > > 09/19/00
>> > > > 09:42PM >>>
>> > > > Why do say that OSPF demand circuit won't cut it?
>> > > > The key to using demand circuit is
>> > > >
>> > > > 1. Define the bandwidth on the BRI interface to
>> > > be
>> > > > less that serial interface
>> > > > 2. If doing any redistribution on either of the
>> > > BRI
>> > > > routers
>> > > > filter such that IP subnet between the two BRI
>> > > > router
>> > > > interfaces doesn't get redistributed. If you
>> > > let
>> > > > this route
>> > > > through the BRI interface will flap because of
>> > > > routing updates.
>> > > > 3. Define OSPF demand circuit on only one router
>> > > > (optional).
>> > > >
>> > > > The other two methods to do this is like you said
>> > > > dialer watch-list
>> > > > and backup interface.
>> > > >
>> > > > Kevin
>> > > >
>> > > >
>> > > > >
>> > > > > Hey bud, got a good config for the following ?
>> > > > >
>> > > > > s0 & bri0 are in the same area 0 of OSPF
>> > > > >
>> > > > > what's a good dial backup config for this for
>> > > when
>> > > > s0 goes down without bri0
>> > > > > flapping? demand circuit doesn't seem to cut
>> > > it,
>> > > > floating statics are out of
>> > > > > the question, leaving only dialer watch-list
>> > > (IOS
>> > > > 12.3 & higher) or backup
>> > > > > interface - but what other way is there if any
>> > > !?
>> > > > >
>> > > > >
>> > > > > Mike L. Chase
>> > > > > Sr. Network Architect
>> > > > > ISG: Information Services Group
>> > > > > Broadcom Corporation World Headquarters, BLDG
>> > > > A-1050
>> > > > > 16215 Alton Parkway, Irvine, California
>> > > > 92618-3616
>> > > > >
>> > > >
>> > >
>> >OFFICE:949-585-6057|CELL:949-283-4254|FAX:949-585-6227
>> > > > >
>> > > > >
>> > > > > -----Original Message-----
>> > > > > From: nobody@groupstudy.com
>> > > > [mailto:nobody@groupstudy.com]On Behalf Of
>> > > > > Kevin Baumgartner
>> > > > > Sent: Tuesday, September 19, 2000 7:10 PM
>> > > > > To: Steve McNutt
>> > > > > Cc: ccielab@groupstudy.com
>> > > > > Subject: Re: Hello, new on list
>> > > > >
>> > > > >
>> > > > > Yes in theory ISDN is simple but I would be
>> > > able
>> > > > to do the following
>> > > > > and have practiced the following on routers.
>> > > > >
>> > > > > 1. OSPF on demand circuit
>> > > > > 2. Dial backup
>> > > > > 3. Appletalk over ISDN (and how to filter so
>> > > ISDN
>> > > > is not up all the time)
>> > > > > 4. IPX over ISDN (also how to filter so ISDN is
>> > > > not up all the time)
>> > > > > 5. Dialer watch
>> > > > > 6. PPP Multilink
>> > > > > 7. PPP CHAP/PAP
>> > > > > 8. PPP Callback
>> > > > > 9. Snapshot routing
>> > > > >
>> > > > > Kevin
>> > > > >
>> > > > > >
>> > > > > > practice ISDN? ISDN is pretty simple to
>> > > > configure and troubleshoot. DOD
>> > > > > > routing using rotary groups and dialer
>> > > profiles
>> > > > gives me fits though hehe.
>> > > > > > If you don't build your configs in the correct
>> > > > order the dialer interfaces
>> > > > > > never seem to work right.
>> > > > > >
>> > > > > >
>> > > > > >
>> > > > > > -----Original Message-----
>> > > > > > From: nobody@groupstudy.com
>> > > > [mailto:nobody@groupstudy.com]On Behalf Of
>> > > > > > Kevin Baumgartner
>> > > > > > Sent: Tuesday, September 19, 2000 9:30 PM
>> > > > > > To: jix@netrue.com
>> > > > > > Cc: ccielab@groupstudy.com
>> > > > > > Subject: Re: Hello, new on list
>> > > > > >
>> > > > > >
>> > > > > > If you don't practice ISDN, ATM or FR you
>> > > have
>> > > > no chance of passing.
>> > > > > > They have to be part of your practice lab.
>> > > > > >
>> > > > > > Kevin
>> > > > > >
>> > > > > >
>> > > > > >
>> > > > >
>> > > > >
>> > > >
>> > >
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