Polycom SOUNDPOINT SIP 3.1 - Manual (Page 315)

Miscellaneous Administrative Tasks
C - 23
Assigning a VLAN ID Using DHCP
To assign a VLAN ID to a phone using DHCP:
>> In the DHCP menu of the Main setup menu, set VLAN Discovery to
“Fixed” or “Custom”.
When set to “Fixed”, the phone will examine DHCP options 128,144, 157
and 191 (in that order) for a valid DVD string.
When set to "Custom", the value set in "VLAN ID Option" will be
examined for a valid DVD string.
DVD string in the DHCP option must meet the following conditions to be
valid:
— Must start with ?VLAN-A=? (case-sensitive)
— Must contain at least one valid ID
— VLAN IDs range from 0 to 4095
— Each VLAN ID must be separated by a ?+? character
— The string must be terminated by a ?;?
— All characters after the ?;? will be ignored
— There must be no white space before the ?;?
— VLAN IDs may be decimal, hex, or octal
For example:
The following DVD strings will result in the phone using VLAN 10:
VLAN-A=10;
VLAN-A=0x0a;
VLAN-A=012;
Note If a VLAN tag is assigned by CDP, DHCP VLAN tags will be ignored.