Vypress Chat works over TCP/IP network protocol and can use IP multicast or broadcast datagrams for communications. Usually such type of traffic is disabled between subnetworks.
There is only one way to get Vypress Chat working over multiple networks it is enabling and configuring routing for multicast network traffic between your networks. You can use any routing protocol to route multicast traffic, for example "Internet Group Management Protocol (IGMP)".
You can find much information about routing for multicast traffic in the Internet by searching keywords “IGMP” or “multicast routing”.
You can also read an article about how to configure IP multicast routing on Windows Server 2008 by following link http://www.vypress.com/products/chat/kb/igmp.aspx