From: Kevin Baumgartner (kbaumgar@xxxxxxxxx)
Date: Thu Sep 21 2000 - 18:59:54 GMT-3
Well it does have something to do with a topology change and this
is getting flood across the ISDN. But the most important item to me
is that if I filter the ISDN network from the redistribution, OSPF demand
circuit works as I would expect. The actually explanation of why this
works I am not clear. Maybe someone that understands demands
circuits and OSPF better than me can explain. Also when I went
through the CCIEbootcamp lab# 8 they had a similar situation where
BGP was redistributed into OSPF. Again the solution was to filter out
the ISDN network from the distribution.
As far as using this in a stub network, this would be the ideal place
to have it. But a question like this could happen in the lab.
Kevin
At 05:38 PM 9/21/00 -0400, you wrote:
>Kevin-
>
>I don't believe that OSPF is only suppressing internal vs external LSAs.
>More specifically, the OSPF router sees the redistribution as a topology
>change and therefore floods the LSA. I didn't look too closely at the
>diagram below to see which router was doing what, but it sounded like the
>ISDN router was the one doing the redist also. That is why it would be
>flooded. Somewhere in one of the Cisco design guides I found a reference
>that demand circuits should be placed in stub areas. This would eliminate
>the problem of the line always staying up.
>
>Now, as to why the engineers made a decision to flood everytime the redist
>process runs, who knows. My guess is that since OSPF is getting info from
>another protocol, it is easier to flood whenever that other protocol sends
>data "over the wall" than to ty to maintain state on which routes are new,
>old, etc.
>
>HTH,
>Joe
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>-----Original Message-----
>From: Kevin Baumgartner <kbaumgar@cisco.com>
>To: Sam Munzani <smunzani@yahoo.com>
>Cc: ccielab@groupstudy.com <ccielab@groupstudy.com>
>Date: Thursday, September 21, 2000 12:24 PM
>Subject: Re: ISDN Problem and OSPF Demand circuit
>
>
> >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 -------
>e0/0 ---- 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
>for 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
>again.
> >
> > 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
>(ISDN Network) into OSPF.
> >Worked like a charm. The ISDN link stayed down and only came up when I took
>the 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
>going 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
>onto 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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