User's Manual

VLAN IDs 475
Each VLAN ID is specified as follows
•
The default VLAN ID is 000 (hex).
• The VOICE and DATA VLAN IDs can be specified in the manual
configuration user interface.
• Or, in the case of the VOICE VLAN ID, the VOICE VLAN ID can also
be configured by the DHCP parameter when using the Automatic
VLAN discovery using DHCP approach.
Automatic VOICE VLAN ID configuration
As part of the 802.1Q feature, there is an option to automatically discover
the VOICE VLAN ID using DHCP. This process reduces the configuration
steps since entering data manually (the VOICE VLAN ID) is not required.
When the Automatic VOICE VLAN Discovery using DHCP approach is
used, and the IP Phone has been configured as such, the following steps
are automatically taken to obtain the VOICE VLAN ID
1. The IP Phones perform an initial DHCP Discovery Request in the
default VLAN.
2.
The DHCP server returns a DHCP Ack me ssage with an IP address in
the data VLAN and one or more voice VLAN IDs in the vendor-specific
field.
3.
The IP Phone reads and saves the VOICE VLAN IDs.
4.
The IP Phone rejects the DHCP offer (accepts it but immediately gives
up the lease).
5. The IP Phone reboots and sends a DHCP Discovery Request with the
first VLAN ID from the saved list. This is repeated for each VLAN ID in
the list until a response is received.
This works because the Layer 2 switch discards every DHCP Discovery
Request it receives from the IP Phone if the VLAN ID does not match the
VLAN IDs configured on the port. When the IP Phone sends a DHCP
Discovery Request with the port configured VLAN ID, the packet passes
into the network and the DHCP server Ack message is passed back.
When a DHCP Ack message is received, the IP Phone accepts the offer
and saves the IP address and Node IP address.
For about how to implement Automatic VOICE VLAN ID, see Converging
the Data Network with VoIP Fundamentals (NN43001-260).
Nortel Communication Server 1000
IP Phones Fundamentals
NN43001-368 02.07
5 February 2009
Copyright © 2003-2009 Nortel Networks
.