System information

428 Features
This option uses the "reserved for site specific use" DHCP options
(number 128 to 254 – refer to RFC 1541 and RFC 1533) and must be
returned by the DHCP server as part of each DHCP OFFER and ACK
message for the IP Phone to accept these messages as valid.
The IP Phone pulls the relevant information out of this option and uses
it to configure the IP address and so on for the primary and (optionally)
secondary TPS.
Either this site specific option must be present or a similarly encoded
vendor-specific option must be sent (as previously described). For
example, configure the DHCP server to send one or the other – not both.
The choice of using either Vendor Specific or Site Specific options is
provided to enable Windows NT DHCP servers to be used with the IP
Phone. Windows NT servers do not properly implement the Vendor
Specific Option and as a result, Windows NT implementations must use
the Site Specific version.
Format of the DHCP Site Specific field
The format of the DHCP Site Specific field is the same as the format of
the Encapsulated Vendor Specific Sub-option field. See “Format of the
Encapsulated Vendor Specific Sub-option field” (page 425) .
DHCP Auto Discovery must be used only if the telephone and PC are:
• connected to the same Layer 2 switch port through a three-port switch
•
on separate subnets
The DHCP server can be configured to supply the VLAN information to
the IP Phones. The server uses the Site Specific option in the DHCP offer
message to convey the VLAN information to the IP Phone.
Configuring a DHCP Server for VLAN Discovery is optional. This
configuration is done in addition to any done for Full DHCP configuration
and it is required only when configuring the VLAN Auto Discovery.
802.1Q VLAN support is configured using the display interface of the IP
Phones during the initial configuration procedure of the IP Phone.
This method is based on the assumption that the default VLAN will be
the data VLAN and the tagged VLAN will be the voice VLAN. Enter the
voice VLAN information into the data VLAN and subnet’s DHCP server.
Enter the standard IP Phone configuration string into the voice VLAN and
subnet’s DHCP server pool.
Nortel Communication Server 1000
IP Phones Fundamentals
NN43001-368 05.02 26 May 2009
Copyright © 2003-2009 Nortel Networks. All Rights Reserved.
.