
702 Chapter 72 VLAN overview
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The following definition describes the Nortel i2004 specific, Site Specific option. This option uses
the reserved for site specific use DHCP options (DHCP option values 128 to 254) and must be
returned by the DHCP server as part of each DHCP OFFER and ACK message for the i2004 to
accept these messages as valid. The i2004 will pull the relevant information out of this option and
use it to configure the IP phone.
Format of field is: Type, Length, Data.
Type (1 octet):
• Five choices 0x80, 0x90, 0x9d, 0xbf, 0xfb (128, 144, 157, 191, 251).
• Providing a choice of five types allows the i2004 to work in environments where the initial
choice may already be in use by a different vendor. Pick only one TYPE byte.
Length (1 octet): (variable depends on the message content)
Data (length octets):
• ASCII based
• format: VLAN-A:XXX,YYY.ZZZ.
where VLAN-A: uniquely identifies this as the Nortel DHCP VLAN discovery.
— -A signifies this version of this spec. Future enhancements could use -B, for example.
— ASCII , (comma) is used to separate fields.
— ASCII . (period) is used to signal end of structure.
— XXX, YYY and ZZZ are ASCII-encoded decimal numbers with a range of 0-4095. The
number is used to identify the VLAN Ids. A maximum of 10 VLAN Ids can be configured.
NONE means no VLAN (default VLAN).
The DHCP Offer message carrying VLAN information has no VLAN tag when it is sent out from
the DHCP server. However, a VLAN tag is added to the packet at the switch port. The packets are
untagged at the port of the IP phone.
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