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New Member

isdn dial backup


In the cisco doc, I can understand the router "maui-soho-01" will dial to router "maui-nas-05" in case the primary interface fails, and the ospf hello packet will be the interesting traffic to bring up the isdn line.

My question is that the router "maui-nas-05", it is not configured with backup, so the interesting traffic(ospf hello) will always try to dial the counterpart router, although it will fail. Is this true? Do I need to define ospf as un-interesting traffic on router "maui-nas-05".

Thanks you.


New Member

Re: isdn dial backup

1) The bri0 interface on maui-soho-01 will be forced and kept down as long as s0 is up/up.

2) With maui-soho-01 conf, any ip traffic will establish dial (if not connected already), and reset the idle timer (set to 900 seconds on both sides, 120 by default).

3) With maui-nas-05 conf, it does not have a phone number to attempt to dial out. The purpose of the map statement is to establish the route based on the other side's authenticated username (router name). However, dialers don't attempt a dial out if there's an established connection already. The purpose of the dialer-group command on maui-nas-05 is to reset the idle timer with any ip traffic going out.

P.S. For OSPF there's a command "ip ospf demand circuit" that can be used in dynamic ituations instead of backup interface configuration if you need OSPF to establish dial out whenever there's a topology change to update area database.

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