Two IPs for each virtual server ?

Hi

My server needs to migrate from one network to an other one in the same datacenter. My hoster advices to add the new ip, configure my services to work with this new ip, then updates DNS to point domains to the new ip, and once everything is ok, remove the old ip of network config of my server.
But I have one issue: I have added the new IP in Linux, it appears in Virtualmin and I added it at the config of Virtualmin but how to tell Virtualmin to handle the virtual servers on both IPs ?

Thanks,

Vincèn