IP Phones in Discovery
by DougR on May.19, 2008, under Best Practices, IP Office
Ever see an IP Phone that shows Discovery on the display followed by an IP Address? This is indicative of bad communication between the IP Phone and the Gateway (IP Office in this scenario). IP Office uses the H.323 protocol for communication, so this article will be based mainly on H.323, SIP will be different.
In the registration process the IP Phone will send a Gatekeeper Request (GRQ) to IP Office control unit acting as the Gatekeeper. The Gatekeeper responds with an packet that acknowledges the phone, lists abilities, and prompts the phone to continue. The phone then sends a Registration Request (RRQ) to the Gatekeeper, and the login continues.
When this process is broken, the phone can not confirm the Gatekeeper or it’s identity, thus the phone is still in the process of discovery for the Gatekeeper. Several things to check:
- IP Addresses
- IP Routes
- Firewalls
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