Avaya Nortel Communication Server 1000 Manual page 189

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DHCP requirements
Some implementation requirements of the Automatic VLAN Discovery using
DHCP are:
1. A DHCP server IP address pool must exist for each subnet (also VLAN).
2. A DHCP server should not exist in more than one VLAN at one time (one
3. Voice and data subnets must be separate if the three-port switch with
4. A Layer 3 switch (or router) with a relay agent must be used because
5. At least two IP address pools are used on the DHCP server – one
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When 802.1Q is enabled, separate voice and data VLAN can be
configured. Each VLAN has its own ID and priority on the IP Phone.
Voice packets have the priority bits of all frames set to 6 (octal) and
the VOICE VLAN ID is set to 000 (hex) by default. Data packets
have the priority bits of all frames set to 0 and the DATA VLAN ID
is set to 000 (hex) by default. The GUI and TPS configured values
override these values.
The IP Phone Ethernet driver receives any Ethernet frame destined
for it, regardless of whether 802.1Q is enabled or the received frame
is an 802.1Q tagged frame.
The only exception is any 802.1Q tagged frame with CFI = 1. In
this case, the frame is discarded.
The IP Phone Ethernet driver strips the 802.1Q tag information from
the frame before passing it on to the IP stack.
The IP Phone Ethernet driver filters the packets by the VLAN tag
and MAC address. Tagged traffic is prioritized and routed based
on the priority bits.
This is standard DHCP operation. The requirement is the same for PC
or IP Phones.
subnet for each VLAN), unless the link to the DHCP server is tagged
and the DHCP server can recognize this. With an untagged link to the
DHCP server, traffic could originate on one VLAN and end up on the
other VLAN. In this case, the VLAN using DHCP feature does not work.
VLAN is being used.
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.
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
Nortel Communication Server 1000
IP Line Fundamentals
NN43100-500 02.02 Standard
Release 5.5 4 February 2008
—End—
802.1Q support 189