Allied Telesis AT-S79 manual Drawbacks Port-based VLANs

Chapter 7: Virtual LANs

Drawbacks of

Port-based

VLANs

ˆEach port must be assigned a PVID. This value must match the VLAN’s VID and it must be the same for all the ports in a port-based VLAN. You must manually configure this value on a port after you assign the port to a VLAN. For instructions, refer to “Configuring the PVID of Untagged Ports” on page 87.

ˆA 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.

ˆIf 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.

ˆThe switch can support up to a total of 256 port-based and tagged VLANs.

There are several drawbacks to port-based VLANs:

ˆIt 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.

ˆA 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.

76 Section I: Using the Menus Interface