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New Member

Failover between 2620 (E1 service) and 1720 (ISDN service)

We have two connections to our ISP - Primary : 2620 with G.703 card to E1 service, and Secondary : 1720 with ISDN BRI (128 k). Both routers perform NAT (private IP inside / public IP outside), and our ISP provides BGP route failover for the block of public IP addresses assigned to our account (between E1 and ISDN services).

How can we setup failover to the ISDN service in event of the E1 service failing ? Do we have to move the ISDN service to a new BRI interface on the 2620, or can we still provide failover using BOTH routers ?

New Member

Re: Failover between 2620 (E1 service) and 1720 (ISDN service)


it is for sure possible to usel both routers. The best way to do so, is to use HSRP on both

routers. in case that the E1 goes down the HSRP process can increase the HSRP priority

on the cisco 2620 and the cisco 1720 will become the activ route. For HSRP configuring

check on CCO:

There are for sure more possibilities available (e.g. floating static routing)

regards Ulrich Marzoli

New Member

Re: Failover between 2620 (E1 service) and 1720 (ISDN service)

How does HSRP affect the routers if they are running NAT - both dynamic and static translations, and CBAC ?? I guess the NAT configuration must be the same on each router, but I am not sure about CBAC ??

New Member

Re: Failover between 2620 (E1 service) and 1720 (ISDN service)


I'm also not quite sure about CBAC but I guess both must be the same. For sure you will lose

the current connectionsin case of a failover because there will be no statefull failover with


Maybe you can use the "ip redundancy" feature to configure statefull failover. It seems at least

be possible:

but I was never used to use it.

regards Ulrich Marzoli

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