DHCP Processing

The IP telephone sends a request to the DHCP server and invokes the DHCP process.

1. The telephone displays one of the following messages:

where s is the number of seconds that have elapsed since DHCP was invoked. The message on the left appears if 802.1Q tagging is off and access to local programming procedures is not disabled or restricted. (See Chapter 3: Local Administrative Options for specifics.) The middle message appears if 802.1Q tagging is on and access to local programming procedures is disabled or restricted. If the left and middle messages alternate every two seconds, 802.1Q tagging is on. When both messages alternate, access to local programming procedures is not disabled or restricted. Finally, the message on the right appears if 802.1Q tagging is off and access to local programming procedures is disabled or restricted.

2. The DHCP server provides IP Addresses for the following hardware:
• The IP telephone
• The TFTP or HTTP server
• The TN799B, C, or D Control-LAN (C-LAN) circuit pack on the media server (for IP telephones supporting H.323 protocol)

The 4601 and 4601+ cannot display messages. Therefore, if the DHCP process locates the required information, the 4601’s Call Appearance Line b indicator flashes continuously 500 milliseconds on, 500 milliseconds off while all other LEDs remain lit. If the appropriate information cannot be discerned or is missing, the 4601’s Call Appearance Line a indicator flutters 50 milliseconds on, 50 milliseconds off three times while all other LEDs remain lit, and a reset occurs.

3. Using the list of gateway IP Addresses provided by the DHCP server, the telephone performs a router check. The telephone cycles through the gateway IP Addresses with ARPs or pings until it receives a response. During this search, the 4601’s Call Appearance Line b indicator flashes continuously 500 milliseconds on, 500 milliseconds off. All other 4601 LEDs remain lit.

When the router is located, the TFTP or HTTP process starts. If no router is found for a 4601/4601+ IP Telephone, its Call Appearance Line b flutters 50 milliseconds on, 50 milliseconds off three times. All other 4601 LEDs remain lit, and a reset occurs.