Information Technology Reference
In-Depth Information
IP Phone Registration Process
The steps that each phone goes through as it registers and becomes operational are more
complex than you might think. The following section reviews these steps:
Key
To p i c
1.
The phone obtains power (PoE or AC adapter).
2.
The phone loads its locally stored firmware image.
3.
The phone learns the Voice VLAN ID via CDP from the switch.
4.
The phone uses DHCP to learn its IP address, subnet mask, default gateway, and
TFTP server address. (Other items may be learned also.)
5.
The phone contacts the TFTP server and requests its configuration file. (Each phone
has a customized configuration file named SEP<mac_address>.cnf.xml created by
CUCM and uploaded to TFTP when the administrator creates or modifies the phone.)
6.
The phone registers with the primary CUCM server listed in its configuration file.
CUCM then sends the softkey template to the phone using SCCP messages.
Note:
What is in that SEP<mac_address.cnf.xml file?
The file contains a list of CUCM server, in order, that the phone should register with. It lists
the TCP ports it should use for SCCP communication. It also lists the firmware version for
each device model and the service URLs that each device should be using.
The CUCM server sends other configurations, such as DNs, softkeys, and speed dials, via
SCCP messages in the last phase of the registration process.
SIP Phone Registration Process
SIP phones use a different set of steps to achieve the same goal. Steps 1 to 4 are the same
as SCCP phones. The following are the rest of the steps:
1.
The phone contacts the TFTP server and requests the Certificate Trust List file (only
if the cluster is secured).
2.
The phone contacts the TFTP server and requests its SEP<mac_address>.cnf.xml con-
figuration file.
3.
The phone downloads the SIP Dial Rules (if any) configured for that phone.
4.
The phone registers with the primary CUCM server listed in its configuration file.
5.
The phone downloads the appropriate localization files from TFTP.
6.
The phone downloads softkey configurations from TFTP.
7.
The phone downloads custom ringtones (if any) from TFTP.
Preparing CUCM to Support Phones
Before we add phones, a certain amount of work should be done on the CUCM servers.
Doing this setup work makes adding phones easier, more consistent, and more scalable,
assuming that we follow our design plan.
