Use the AV2 as the master, then drop a RACK2 in your crestnet devices as a Crestnet slave since you have no E-NET card. In the Rack2 info view in toolbox, you'll see where it has a Crestnet ID of "2". You need to change that to some other Crestnet ID (3 or higher) and it will show up on your AV2 crestnet network.
Goodluck,
Cyberbri