How is hunting enabled if we have the phone book in the Gatekeeper and not in the host VOIP?

Each VOIP maintains a phonebook for its own channels only when used in gatekeeper mode, rather than having one host maintain the phonebook for the entire voip network. Each voip then uses its own entry's to register with the gatekeeper. To hunt between VOIPs, you would assign a common H.323 ID in the phone entries. This H323 id would be used as a gatekeeper service defined in the gatekeeper setup. When the VOIPs register, the channels that support this service would hunt.