Allied Telesis AT-S63, Features Manual

Page: 274 / 538

Chapter 24: Port-based and Tagged VLANs
274 Section VI: Virtual LANs
three AT-9400 Switches, you would assign the Marketing VLAN on each
switch the same VID.
You can assign this number manually or allow the AT-S63 Management
Software to do it automatically. If you allow the management software to
do it automatically, it selects the next available VID. This is acceptable
when you are creating a new, unique VLAN.
If you are creating a VLAN on a switch that will be part of a larger VLAN
that spans several switch, then you will need to assign the number
yourself so that the VLAN has the same VID on all switches.
Untagged Ports
You need to specify which ports on the switch are to be members of a
port-based VLAN. Ports in a port-based VLAN are referred to as
untagged
ports and the frames received on the ports as untagged frames . The
names derive from the fact that the frames received on a port will not
contain any information that indicates VLAN membership, and that VLAN
membership will be determined solely by the port’s PVID. (There is
another type of VLAN where VLAN membership is determined by
information within the frames themselves, rather than by a port’s PVID.
This type of VLAN is explained in “Tagged VLAN Overview” on page 279.)
A port on a switch can be an untagged member of only one port-based
VLAN at a time. An untagged port cannot be assigned to two port-based
VLANs simultaneously.
Port VLAN
Identifier
Each port in a port-based VLAN must have a port VLAN identifier (PVID).
The switch associates a frame to a port-based VLAN by the PVID
assigned to the port on which the frame is received, and forwards the
frame only to those ports with the same PVID. Consequently, all ports of a
port-based VLAN must have the same PVID. Additionally, the PVID of the
ports in a VLAN must match the VLAN’s VID.
For example, if you were creating a port-based VLAN on a switch and you
had assigned the VLAN the VID 5, the PVID for each port in the VLAN
would need to be assigned the value 5.
Some switches and switch management programs require that you assign
the PVID value for each port manually. However, the AT-S63
Management Software performs this task automatically. The software
automatically assigns a PVID to a port, making it identical to the VID of the
VLAN to which the port is a member, when you assign the port as an
untagged member to a VLAN.