Allied Telesis AT-S39 - Manual (Page 123)

AT-S39 User’s Guide
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For example, assume that you were creating a port-based VLAN on a
switch and you had assigned the VLAN the VID 5. Consequently, 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-S39
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.
General Rules for Creating Port-Based VLANs
Below is a summary of the general rules to observe when creating port-
based VLANs.
❑ 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 must be assigned the same VID.
❑ A port can be an untagged member of only one port-based VLAN
at a time.
❑ Each port must be assigned a PVID. This value is assigned
automatically by the AT-S39 management software. The value is
the same for all ports in a port-based VLAN and is identical to the
VLAN’s VID.
❑ A port-based VLAN that spans multiple switches requires a port
on each switch where the VLAN is located to function as an
interconnection between the switches where the various parts of
the VLAN reside.
❑ If there are end nodes in different VLANs that need to
communicate with each other, a router or Layer 3 switch is
required to interconnect the VLANs.
Drawbacks to Port-based VLANs
Drawbacks to port-based VLANs:
❑ Sharing network resources, such as servers and printers, across
multiple VLANs can be difficult. A router or Layer 3 switch must be
added to the network to provide a means for interconnecting the
port-based VLANs. The introduction of a router into the network
can create security issues, including unauthorized access to your
network.
❑ A VLAN that spans several switches requires a port on each switch
for the interconnection of the various parts of the VLAN. For