From: Bruce Evry (bruceco@xxxxxxxxxx)
Date: Wed Jun 06 2001 - 14:18:11 GMT-3
Dear David,
I've had hours of fun fighting with Flapping ISDN.
On an OSPF Demand Circuit you have to be very careful.
If one side of the Demand Circuit is redistributing, say for
example, IGRP into OSPF, even if you make the ISDN a passive interface,
IGRP will still monitor the interface and send a notice out if it goes
down. (of course with an OSPF Demand-circuit the interface is supposed to
go down....)
Worse yet, even if you filter out the Routes going into OSPF so
that they do not appear in your routing table, they still get put into the
OSPF database, which is what gets sent out to all your other routers.
(which then helpfully calculate things out based on that data so
that it tells it "hey, that ISDN interface just went down - I'd better
bring up the Demand-circuit so that it can recalculate its routes, eh?)
The trick seems to be to set up a Summary-address under OSPF that
includes the ISDN ip addresses.
Router OSPF 1
summary-address 172.20.96.0 255.255.255.0
network 172.20.96.0 0.0.0.3 area 0
This gives OSPF a stable logical network summary-address that
should keep your lines from flapping.
Yours Truly - Bruce Evry
(Lab, try 2, next Monday....)
On Tue, 5 Jun 2001, David Anderson wrote:
> Hi,
> I am having an issue with my ISDN line flapping. I have ip ospf demand
> circuit and I am blocking any redistributed routes but the line is still
> going up and down. When I use the show dialer command to see the cause of
> the line going up it has the source as the ip address of the BRI interface
> and the destination to the other ends ip address of the BRI interface.
>
> EX.
>
> R1(BRI0)---------------------------(BRI1/0)R2
> 133.1.100.5/30 133.1.100.6/30
>
> sh dialer map
> dialing cause
> 133.1.100.5---133.1.100.6 ??????
>
> Any thoughts as to what this is?
>
> Thanks,
> David
> David Anderson
> Network Design Engineer
> Enterprise Solutions Architecture & Design
> (408) 853-5515
> dma@cisco.com
> | |
> ..:|||||||:...:|||||||:..
> C I S C O S Y S T E M S
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