Allied Telesis AT-S39 - Manual (Page 123)

AT-S39 User’s Guide
123
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 an untagged 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
example, a VLAN that spans three switches requires one port on
each switch to interconnect the various sections of that VLAN.