Polycom SOUNDPOINT SIP 3.1 - Manual (Page 316)

Administrator’s Guide SoundPoint IP / SoundStation IP
C - 24
The following figure shows the phone’s processing to determine if the VLAN
ID is valid:
Parsing Vendor ID Information
After the phone boot, it sends a DHCP Discover packet to the DHCP server.
This is found in the Bootstrap Protocol/option “Vendor Class Identifier”
section of the packet and includes the phone’s part number and the bootROM
version. The format of this option's data is not specified in RFC 2132, but is left
to each vendor to define its own format. To be useful, every vendor's format
must be distinguishable from every other vendor's format. To make our
format uniquely identifiable, the format follows RFC 3925, which uses the