Specifications

Engineering Guidelines
240
5302 Startup and DHCP
DHCP options will be used to inform the 5302 of servers that can be contacted to register and
retrieve the profiles.
RFC 3925, Vendor-Identifying Option exchange (options 124/125) will be used as the primary
mechanism for conveying the addresses of these servers.
The 5302 will transmit a DHCP discover message containing the option 55 (Parameter Request
List). Within the request list, each endpoint will include option 124 (Vendor Class Identifier).
Option 124 will be used in the parameter request list as the primary method of specifying the
vendor-specific information. This option solicits retrieval of option 125, vendor-specific
information, which is returned by the server.
Option 125 will include the address of the 3300 ICP that is to be used as the primary SIP contact
point (REGISTRAR). Additional information may be included, such as Layer 2 priority, voice
LAN identification (VLAN) and QoS (DSCP), which is used to define packet priority for the IP
layer. When these tags are presented in the option 125 response, they will override any
associated values found within the local-network or device profile.
Startup Sequence for the Controller
The controller startup sequence involves bringing up the RTC where call control resides. This
also includes the local DHCP and TFTP servers.
In order to correctly program some of the options within DHCP, such as the RTC and TFTP
server, it is necessary to pre-assign an IP address to the 3300 ICP. This address is used by
the IP networking handler and is entered into the database of other remote ICP units.
The DHCP server in the 3300 ICP controller should be used for local devices on the voice
VLAN. This can be disabled, but then an external DHCP server is required to service devices
on the voice VLAN.
Where multiple DHCP servers are used on a LAN, for example in a redundant or load balancing
situation, the information in the different servers must be consistent for all the phones to start
up correctly.
Mitel Communication Director
The Mitel Communication Director does not support an integral DHCP server. The 3300 internal
DHCP server can be used if a 3300 ICP is included in the installation. Otherwise a third party
DHCP server must be provided.