While trying to configure the inter-array IP on the server object under “System” in ForeFront TMG management console, you may get an error message says:

“The IP Address specified for intra-array communication is not a valid intra-array IP address.The IP address used for intra-array communication must belong to a defined network object”

Well, you need to create a new Network “object” under “Networking” for the intra-arrray selected NIC’s then configure.

HTH