Enhanced Vlan Tagging - Nortel 1110 Fundamentals

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
2. The DHCP server returns a DHCP Ack me ssage with an IP address in
3. The IP Phone reads and saves the VOICE VLAN IDs.
4. The IP Phone rejects the DHCP offer (accepts it but immediately gives
5. The IP Phone reboots and sends a DHCP Discovery Request with the
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.

Enhanced VLAN Tagging

Enhanced VLAN has two main functions
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VLAN filtering on the telephony port is disabled by default. If tagging is enabled
on the telephony port, you can enable VLAN filtering on the telephony port. When
VLAN filtering is enabled, packets destined for the IP Phone port are filtered
based on the MAC address and the VLAN tag.
If VLAN filtering is not enabled on the telephony port, packets destined for the IP
Phone port are filtered only on the MAC address. Filtering based on the VLAN tag
does not occur. This makes the telephony port susceptible to broadcast storms
and a Denial of Service (DOS) attack.
Copyright © 2003–2007, Nortel Networks
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default VLAN.
the data VLAN and one or more voice VLAN IDs in the vendor-specific
field.
up the lease).
first VLAN ID from the saved list. This is repeated for each VLAN ID in
the list until a response is received.
Enhance the current Voice VLAN by implementing the hardware VLAN
filter on the IP Phone port (SMP).
Use TX High Priority Queue (HPQ) and 802.1P VLAN priority to
enhance the traffic control on the IP Phone and PC network interface.
Nortel Communication Server 1000
IP Phones Fundamentals
NN43001-368 01.02 Standard
Release 5.0 20 June 2007
ATTENTION
VLAN IDs 451