VidyoGateway - You have entered an invalid room extension - error when integrating with Cisco Call manager

VidyoVoice users receive the IVR error message "you have entered an invalid room extension"

The Call Manager is most likely appending a number to the SIP invite that is different than what is expected by the VidyoGateway .

A SIP Invite usually consists of [Alias]@[IP/FQDN] .  What we want is for the  Call Manager to send a SIP Invite to the VidyoGateway  in the form of [Service Prefix@IP of GW].

For example: if one creates a Voice-Only FROM LEGACY Prefix on the VidyoGateway and set it to 63, we want the Call Manager to forward a SIP Invite in the form 63@198.16.25.23. This will connect to the voice-only IVR, once at the IVR enter a user extension, the VidyoGateway transforms the Invite to     63{Extension]@198.16.25.23, thus connecting to the Vidyo user's virtual room.