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AT-S79 Management Software User’s Guide
Section I: Using the Menus Interface 81
Note
For explanations of VLAN name and VLAN identifier, refer back to
“VLAN Name” on page 74 and “VLAN Identifier” on page 74.
Tagged and
Untagged Ports
You need to specify which ports will be members of the VLAN. In the case
of a tagged VLAN, the ports usually consist of both untagged and tagged
ports. You specify which ports are tagged and which untagged when you
create the VLAN.
An untagged port, whether a member of a port-based VLAN or a tagged
VLAN, can be in only one VLAN at a time. However, a tagged port can be
a member of more than one VLAN. A port can also be an untagged
member of one VLAN and a tagged member of different VLANs
simultaneously.
Port VLAN
Identifier
As explained earlier in the discussion on port-based VLANs, the PVID of a
port determines the VLAN where the port is an untagged member.
Because a tagged port determines VLAN membership by examining the
tagged header within the frames that it receives, you could conclude that
there is no need for a PVID. However, the PVID is used if a tagged port
receives an untagged frame — a frame without any tagged information.
The port forwards the frame based on the port’s PVID. This is only in
cases where an untagged frame arrives on a tagged port. Otherwise, the
PVID of a tagged port is ignored.
Guidelines to
Creating a
Tagged VLAN
Below are the guidelines to creating a tagged VLAN.
Each tagged VLAN must be assigned a unique VID. If a particular
VLAN spans multiple switches, each part of the VLAN on the different
switches must be assigned the same VID.
A tagged port can be a member of multiple VLANs.
An untagged port can be an untagged member of only one VLAN at a
time.
The switch can support up to a total of 256 port-based and tagged
VLANs.