Allied Telesis AT-S63 - Manual (Page 432)

Chapter 19: Port-based and Tagged VLANs
432 Section III: VLANs
General Rules
for Creating a
Port-based
VLAN
Below is a summary of the general rules to observe when creating a port-
based VLAN.
❑ 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.
❑ 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 must be the same
for all ports in a port-based VLAN and it must match the VLAN’s
VID. This value is automatically assigned by the AT-S63
management software.
❑ 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 of
Port-based
VLANs
There are several drawbacks to port-based VLANs:
❑ It is not easy to share network resources, such as servers and
printers, across multiple VLANs. 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 your network
could create security issues from 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 would require one
port on each switch to interconnect the various sections of the
VLAN. In network configurations where there are many individual
VLANs that span switches, many ports could end up being used
ineffectively just to interconnect the various VLANs.