[LeonidasG]

We have setup two virtual servers using Vmotion to sync each server with an auto failover using the VM utilities to achieve this scenario, however it would be nice if an automated restore to a second windows system could be done also.

I havent tried Vmotion yet, does it also Replicate the IP of the other machine?
If your Main Server goes down, sure you have a second server ready to work, but what about the phones themselves? You would need to manually point them all to the new server right?

[netswork]

Vmotion migrates the running state from one physical server to another...it will maintain IP's and MAC addresses. In newer versions of vmware you can have a running replica of an existing virtual machine, it maintains memory state of the active machine in the replica. If the physical ESXI server were to crash or loose power or what ever the replica would take over. It requires Enterprise license of vmware, which is not cheap. But if this was a large enterprise and phones are mission critical it would be a good solution.

[eagle2]

Wouldn't be possible a router to switch a failed server to backup one (using some scripts and suitable NAT).
This includes the IP address to which phones register (i.e. 3CX server) -- that address is not changing, port forwarding (for external extensions and providers). Some more expensive systems (like Cisco UCM, Avaya Aura) do this automatically in case of failure of primary server.

Regards

[netswork]

If you were using vmware the IP address of the Virtual machine would remain the same. So if you had two vmware servers using high availability and one server crashed, the system would continue running on the other server using the same IP address.

All routers and firewalls would not know anything happened and calls would continue as normal.