Exceptions To The Vlan Forwarding Rules; Special Considerations - Avaya J129 Installing And Administering

• Configure one of the following for egress tagging:
- Data VLAN is untagged and voice VLAN is tagged.
- Data VLAN and voice VLAN are both tagged. You must configure this option to have Full
VLAN separation.
Sending egress voice VLAN frames untagged from the external switch port to the phone LAN port
means that there is no VLAN separation between the voice VLAN and data VLAN.

Exceptions to the VLAN forwarding rules

Exceptions to the VLAN forwarding rules are as follows:
• LLDP frames are always exchanged between the LAN port and CPU port and CPU port and
LAN port in all VLAN separation modes.
• Spanning tree frames are always exchanged between the LAN port and PC port in all VLAN
separation modes.
• 802.1x frames are always exchanged between the LAN and CPU port or PC port, between the
PC to CPU port or LAN port and between the CPU port to LAN port in all VLAN separation
modes according to DOT1XSTAT and DOT1X configuration.

Special considerations

Special use of VLAN ID of zero
In some configurations it is desirable to utilize the priority functionality of the VLAN frame only and
not utilize the VLAN ID properties. In this scenario the phone will add a VLAN tag to the egress
voice frames with a VLAN ID = 0 and a priority of the value set by the L2QAUD parameter or
L2QSIG parameter.
Automatic failback of VLAN tagging (VLANTEST)
The phone has a functionality that connects the phone to a network when the value of L2QVLAN
does not match with the VLAN being assigned to the network access switch. When the phone starts,
it attempts to contact the DHCP server with a VLAN ID= L2QVLAN. If the phone does not receive a
DHCPOFFER with that particular VLAN ID, then it eventually falls back. The phone attempts the
DHCP negotiation again in one of the two ways:
• If the VLAN functionality of the phone is turned on (L2Q=1): With a VLANID =0
• If the VLAN functionality of the phone is set to automatic (L2Q=0): Without any VLAN tag.
The parameter that determines how long the phone will wait for a recognizable DHCPOFFER is
defined by the VLANTEST parameter. If VLANTEST= 0 then the phone does not failback and keep
sending DHCP request using tagged VLAN frames with VLAN ID = L2QVLAN.
Computer port (PC port) VLAN support
The phone only supports one VLAN on the Computer (PC) port, which is the data VLAN, in Full
VLAN separation mode. In No VLAN separation mode all VLANs passes between LAN and PC port.
However, the CPU port in this case receives all traffic even on VLANs which are not equal to
L2QVLAN.
September 2017 Installing and Administering Avaya J129 IP Phone
Comments on this document? infodev@avaya.com
Virtual LAN (VLAN) overview
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