The NetVanta 7100 currently doesn’t support Bridge/Shared Extension Currently right now but is looking to add it as a feature in upcoming release but has not been set yet. Sorry for any inconvenience.
Here are other solutions for your need:
(1) Create an Executive Ring Group
What this does is you put the executive and receptionist in the ring group, when someone calls the executive, both phones ring but if no one answers, the call coverage goes to the executive. You can also create a caller ID Prefix so the receptionist knows the call is for the boss and not for the receptionist extension
(2) Use Pickup Extension
When the Executive Extension rings, the receptionist can pick it up by dialing *52. So if executive extension is 5001, then the receptionist would dial *525001. That number could be programmed as a speed dial on her phone.
Hope that helps. Let me know if you have any questions.