TFTP

Devices such as Cisco IP phones require TFTP to retrieve configuration files and other information.

TFTP is crucial to the correct operation of a CUCM network, so it is recommended that DHCP option 150 be used because it allows TFTP server redundancy to be configured. Cisco also recommends that option 150 be used to specify differently ordered lists of TFTP server addresses to hosts on different subnets to provide load balancing.

To better understand the importance of TFTP in a CUCM network and the significance of DHCP option 150, it is a good idea to examine Cisco IP phone initialization and registration.

Cisco IP phone initialization and registration involves the following:

1. Assuming that the phone is not using its own power supply, the phone powers itself using inline power. If the Cisco IP phone is connected to a switch that supports power over Ethernet (PoE), the switch detects the phone and applies power to the corresponding Ethernet port.