You can't create such a hunt group because when you configure a line group in CUCM then you cant see extension of another cluster. But you can achieve this using remote destination profile, please visit below link for such configuration.
Thank you for the link- I followed all the steps and I was able to get the U.S extensions
to ring, however I was not able to get the UK extensions to ring when I called the hunt pilot number.
Any idea what may have caused this ?
I followed all the steps below.
1. Create a dummy DN (need not be associated with any phone) by browsing to Call Routing > Directory Number
2. Create a Line Group (Call Routing > Hunt / Route > Line Group), and assign the dummy DN as a hunt group member.
Add other members to the Line Group, as needed.
3. Create a Hunt List (Call Routing > Hunt / Route > Line Group) and associate the Line Group with it
4. Associate this Hunt List with the required Hunt Pilot Number5. Create Remote Destination Profile (Device > Device Settings > Remote Destination Profile) with its line being
the dummy DN
6. Create a Remote Destination (RD) to the cell phone you want the call to be extended to, and associate it with the
Remote Destination Profile (RDP)
7. Set the Delay Before Ringing timer on RD to be 0, so that the call to the cell phone is extended
immediately when the Dummy DN is called8. Make sure that you check the 'Enable Mobility' checkbox for the RDP user (User Management > End Users)
9. Make sure that the SNR call to the cell phone will be successful (Rerouting CSS on RDP determines that)
I would suggest you to recheck the configuration once more or first try to create a SNR configuration for a Extension and Mobile after that you can configure it for hunt group. There is one more good document for it.