Can we have two ADSL lines with the same static IP addresses.

[momotaro]

Dear Sears,

At our company we have a specific need for two ADSL lines in fail-over mode with the same IP address and preferably from two different ISP.
The reason is that we work remotely with a client that in case of internet breakage logs us out and we have to relog in in order for the system to let us in again.
I know it sound stupid by who knows...

Best regards.

[sicarie]

Only one system can have an IP on a given network. You can have systems (or networks) that mirror each other by NAT, but to do this on the internet you'll either need to have a failover device, or as you said, wait for a breakage and then manually update whatever public facing records so that your backup site is now your main.

A failover device is similar to (or can be) a load balancer, where this device keeps both public IPs, and decides which to send traffic to either by how much traffic it's directing, or through 'heartbeat' messages to test responsiveness of each IP.