Allied Telesis AT-S79, Руководство пользователя

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AT-S79 Management Software User’s Guide
Section I: Using the Menus Interface 75
For example, if you had a port-based VLAN titled Marketing that spanned
three AT-GS950 Series switches, you would assign the Marketing VLAN
on each switch the same VID.
You can assign this number manually or allow the AT-S79 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, you must 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 80.)
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 assign the PVID value automatically when you assign an
untagged port to a VLAN. However, with the AT-S79 management
software you must perform this task manually.
Guidelines to
Creating a Port-
based VLAN
Below are the guidelines to creating a port-based VLAN.
ˆ
Each port-based VLAN must be assigned a unique VID. If a particular
VLAN spans multiples switches, each part of the VLAN on the different
switches should be assigned the same VID.
ˆ
A port can be an untagged member of only one port-based VLAN at a
time.