I was trying to connect from primary test box to my hyperv core test box via the Hyper-V MMC management tools, I kept getting "Access denied. Unable to establish communication between Client and Server".

From the command prompt of your ‘Client’ can do this by typing: ”DCOMCNFG” in the run-command in Windows.

2. Browse trough to: “Component Services > Computers > My Computer”.

3. Open Properties for “My Computer” and select the COM Security tab.

4. In “Access Permissions” area click the “Edit Limits”-button.

5. Select the “Anonymous Logon”-group and make sure the “Remote Access” is set to Allowed.

Now you client tools should connect successfully to the servers Hyper-V management.