Features Page 239 of 910
IP Line Description, Installation and Maintenance
3Voice and data subnets must be separate if the three-port switch with
VLANs is being used.
4A Layer 3 switch (or router) with a relay agent must be used because
traffic from the voice VLAN to the data VLAN must be routed.
Presumably, the DHCP server is on the data VLAN. Without a relay
agent, a DHCP server must exist on each subnet.
5At least two IP address pools are used on the DHCP server – one for the
Voice VLAN/subnet and another for the Data VLAN/subnet. Additional
pools can be added as required as long as one IP address pool per subnet
and VLAN is used. A relay agent is required if it is a PC-only network.

Control of the IP Phone’s 802.1Q

The 802.1Q header in the outgoing packets from the IP Phones is enabled by
one of the following:
• If the IP Phone’s VLAN GUI response is set to 1, then the 802.1Q
functionality is enabled. All packets from the IP Phone have the 802.1Q
header as part of the Ethernet frame.
• If the IP Phone’s VLAN GUI response is set to 2, then the 802.1Q
functionality is enabled after the DHCP response is received with the
VLAN ID.
• If the OTM or Element Manager configuration enables the use of the “p”
bits, once downloaded to the IP Phone, the 802.1Q functionality is
enabled.

802.1Q and the Voice Gateway Media Cards

The ITG-P 24-port and Media Card line cards cannot send the 802.1Q header
because the cards’ operating system does not support it. The switch ports
connecting the Voice Gateway Media Card’s TLAN network interface should
be configured for untagged operation so if a 802.1Q header is present, it is
stripped before a packet is passed to the card.
The configuration in OTM and Element Manager is for the control of the
priority bits in the 802.1Q header sent by the IP Phones only.