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OSPF with backup dialer configuration question

I have configured both E1(Primary) and dialer (backup) to use ospf. When the primary interface is active does OSPF show anything for dialer interface in OSPF neighbor or OSPF interface?

The problem that I am facing is that sometimes it doesn't fall back aotomatically when the E1 interface goes down. I am not using backup command or watch list I am just using OSPF to send interesting traffic to dialer if primary interface is down.

Second, if I administratively hut down primay and fire ISDN manually then even if I bring up the primary interface the status for primary interface shows down down. I have to manually shut down backup interface to bring primary in UP status. Any ideas are appreciated.

Thank you


Re: OSPF with backup dialer configuration question


A floating static route with higher admin distance like 120 or so coz the admin distance of ospf is 110 will do the trick.

we have seen some locations working fine with the same kinda configs..

are you having any static route with higher admin distance ?

is it possible to post out the config ?


Hall of Fame Super Gold

Re: OSPF with backup dialer configuration question

I do not understand very well the symptom that the original post is explaining. Some more detail would be helpful. Also seeing the specifics of how both interfaces are configured would help and whatever mechanism is being used to accomplish the failover.

I would also suggest that it might be good to consider OSPF demand circuit for this environment. With demand circuit OSPF will bring up the dial link to establish neighbor relationship and then will let the link go inactive and hang up. OSPF does maintain the neighbor relationship with the neighbor over the dialer but does not send the periodic hello messages. Especially if you adjust the OSPF cost of the dialer interface then OSPF will see the primary interface as better and the dialer interface as a backup.



New Member

Re: OSPF with backup dialer configuration question


as mentioned in earlier post floating static routes do work.

I used the OSPF demand circuit and still as soon as dialer interface disconnects OSPF doesn't show any neibor on this interface and shows the dialer as down in show ip OSPF interface.

I am not sure if it is the expected behavior. My initial question is concerned to the same issue. Does OSPF show the dialer interface in OSPF neighbor, when dialer is idle not dialing and I use command show ip ospf demand-circuit.

Also is it necessary to use ip ospf demand-circuit command on both the dialing and receiving routers.

Re: OSPF with backup dialer configuration question

The OSPF demand circuit neighbor stays up always but the periodic hellos are suppressed.

Use ip ospf demand-circuit on the dialing router ONLY.

Make Sure OSPF multicast packets is included (permitted) in your dialer list (access list) as interesting traffic.



New Member

Re: OSPF with backup dialer configuration question

Hi Sundar,

I did the same thing and for some reason it always keep on dialing and never disconnects eventhough primary link is active.


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