From: tria_ka@gmx.net
Date: Wed Mar 12 2003 - 15:37:45 GMT-3
Brian,
thanks a lot for your detailed informations.
Tonight i will try several methodes.
regards
udo
> Without the configurations it's hard to tell what the exact problem is
> but a possible problem is with RIP telling OSPF about the status of the
> ISDN subnet through redistribution. Try taking off the redistribution of
> RIP into OSPF and see if the link stays quiet.
>
> If the link does stay quiet after redistribution is removed, you should
> look into using a route-map and filter off the ISDN subnet from being
> redistributed into OSPF from RIP. Basically the problem is that every
> time the ISDN link drops RIP informs OSPF through redistribution that
> the ISDN subnet isn't available. Since this causes a change in the OSPF
> database, OSPF has to inform its neighbors. This means that a call
> across the demand circuit has to be placed to notify the OSPF neighbor
> on the other end. Once the link comes back up for OSPF to notify its
> neighbor RIP informs OSPF that the ISDN subnet is again available. All
> is fine till the idle-timeout is reached for the ISDN link and the link
> drops again. This isn't a problem for OSPF because this is a demand
> circuit but now that the ISDN link is down RIP again informs OSPF that
> the ISDN subnet isn't available. This of course causes another change in
> the OSPF database and another call must place to inform the OSFP
> neighbor about the change. This is just a never ending circle as you can
> see.
>
> You should also look into filtering off any /32 host routes that might
> have been installed via PPP from being redistributed into OSPF from RIP.
> Since RIP also supports host routes, RIP will redistribute them into
> OSPF. You can use the "no peer neighbor-route" command if it's not
> already on to stop the /32 host routes from being generated or just
> filter off the /32 in the route-map used for redistribution.
>
> In the future if you ever have to configure an OSPF demand circuit on an
> ASBR watch out for the problems described above ;-)
>
> Brian Dennis, CCIE #2210 (R&S/ISP Dial/Security) CCSI# 98640
> brian@labforge.com
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> tria_ka@gmx.net
> Sent: Tuesday, March 11, 2003 10:30 PM
> To: OhioHondo
> Cc: jhays@jtan.com; ccielab@groupstudy.com
> Subject: RE: isdn - backup - challenge - authentication ???
>
> hi,
>
> > Can it be that changes in the OSPF topology have occured?
> yes that is also what i understand but i don't know why there is a
> change
> every time.
> if i have a look on ip ospf database normally it's really stable. when i
> configure bri on both sides for isdn the link comes up changes lsa, the
> go
> down....and up again....every time...no stopping !!..;-(
>
> > When using OSPF on demand, it is my understanding that the ISDN link
> comes
> > up initially and learns the network.
> >
> > I also have read that every time a change in the topology is sensed,
> the
> > ISDN circuit comes up again to keep itself current with an accurate
> > topology. (When the primary goes down, network operation depends on
> the
> > ISDN
> > routes to be an accurate view of the network. Imagine a primary that
> > hasn't
> > gone down in months. If the ISDN didn't keep updated, it would be
> > worthless
> > as a backup that is meant to give an IMMEDIATE alternate route when
> the
> > primary goes down.)
> >
> > I have also read that OSPF On Demand is not recommended in parts of
> the
> > OSPF
> > network where changes occur frequently --- because the ISDN link will
> keep
> > going up and down. It is recommended that it be used on Stub links.
>
> uuppss that is what i don't try. i also heard there is sometimes a
> problem
> with virtual links ? so there is also a virtual link !!
> keep it the isdn line up ?
>
> thanks
>
> udo
>
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > Jonathan V Hays
> > Sent: Tuesday, March 11, 2003 2:21 PM
> > To: ccielab@groupstudy.com
> > Subject: RE: isdn - backup - challenge - authentication ???
> >
> >
> > > -----Original Message-----
> > > From: tria_ka@gmx.net [mailto:tria_ka@gmx.net]
> > > Sent: Tuesday, March 11, 2003 1:47 PM
> > > To: Jonathan V Hays
> > > Cc: ccielab@groupstudy.com
> > > Subject: RE: isdn - backup - challenge - authentication ???
> > > Hi Jonathan,
> > > thanks. That is what I also know ..,;-)) I can read the debug
> > > output...
> > > But I don't understand WHY this MC packet trigger my isdn
> > > line to go up.
> > > Both isdn bri if's are in the ospf state 'running on demand' !
> > > any comments ? help ??
> > > thanks
> > > udo
> > >
> > > > The dial reason is 224.0.0.5 which is one of the OSPF multicast
> > > > addresses.
> >
> > Udo,
> >
> > Possibly something is not allowing a complete OSPF database
> > sychronization between the two routers. Or maybe it's OSPF
> > authentication that hasn't been configured across a virtual link. It's
> > hard to tell with what little information you have provided.
> >
> > Please post your configuration files for both routers.
> >
>
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