Polycom CX5100 Unified Conference Station for Microsoft Skype for Business - Administrator Guide
Polycom, Inc. 38
Protocol (LLDP) to assign a VLAN ID, it is possible to assign a VLAN ID to the system by distributing the
VLAN ID via DHCP.
When using this method to assign the system’s VLAN ID, the system first boots on the default VLAN (or
statically configured VLAN, if first configured in the system’s network configuration menu), obtains its
intended VLAN ID from the DHCP offer, then continues booting (including a subsequent DHCP sequence)
on the newly obtained VLAN.
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 semi colon “;”
● All characters after the semi colon “;” are ignored
● There must be no white space before the semi colon “;”
● VLAN IDs may be decimal, hex, or octal
The following DVD strings result in the system using VLAN 10:
VLAN-A=10;
VLAN-A=0x0a;
VLAN-A=012;
Parse Vendor ID Information
After the system boots, 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 system’s part number and
the BootROM version. RFC 2132 does not specify the format of this option's data, and can be defined by
each vendor.
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 IANA private enterprise number
to determine which vendor's format should be used to decode the remaining data. The private enterprise
number assigned to Polycom is 13885 (0x0000363D).
This vendor ID information is not a character string, but an array of binary data.
The steps for parsing are as follows:
1 Check for the Polycom signature at the start of the option:
4 octet: 00 00 36 3d
2 Get the length of the entire list of sub-options:
1 octet
3 Read the field code and length of the first sub-option, 1+1 octets
Note: If a VLAN tag is assigned by CDP or LLDP, DHCP VLAN tags are ignored.
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