Backup site for vSZ-H

[raazuko]

We have a vSZ-H running 3.4.0.0.976 at one of Private data centers.We are planning to install another one at a different location as a backup for the existing one.So I have few questions regarding the deployment.
-Do we need additional licenses?
-Do we need to take anything in consideration before deployment or do we deploy it as the previous one and configure it as a slave/backup later?
-What are the requirements for WAN as they would be on different locations and hence different subnet?