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Bring Up Dialer if ISP Interface on Mated Router Goes Down?

Rob Cluett

I have two 3825's. Each has it's own ISP connection. Nat is configued for both. They have an ethernet connection between them and I'm running OSPF between the two so the routes propogate. I have qty 11 Dialer interfaces configured on each router (each router has an exact copy of the other routers dialer interface). However, I only want the Dialers up if the ISP connection on the mated router goes down. Much like HSRP I need one to preempt and be active if both ISP connections are up. When one goes down the other Dialers must come up. Each dialer sends a Dynamic DNS host name and IP address pair to So I cannot have both up otherwise the DNS names will bounce between ISP#1's IP address and ISP#2's IP address (back and forth). Let me know if any option exists to make this happen. As an aside the ISP's are providing me DHCP addresses so I cannot work off of an IP, it has to be the physical interface (i.e. Gi0/0).

1 Reply 1

Giuseppe Larosa
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

Hello 2rcluett.

the dialer-watch may be the right tool to use here as it checks the IP routing table for presence of some routes.

if the monitored routes disappear a call is triggered.

I have used this successfully with ISDN DDR but it should work with dialer interfaces.


A routing protocol is required between the two routers and you have OSPF-

Hope to help


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