KB.15.15

Example 43 VLAN ID numbers assigned in the VLAN names screen

VLAN tagging considerations:

• Since the purpose of VLAN tagging is to allow multiple VLANs on the same port, any port

that has only one VLAN assigned to it can be configured as "Untagged" (the default) if the

authorized inbound traffic for that port arrives untagged.

• Any port with two or more VLANs of the same type can have one such VLAN assigned as

"Untagged." All other VLANs of the same type must be configured as "Tagged," that is:

Protocol VLANsPort-Based VLANs

A port can be an untagged member

of one protocol-based VLAN of each

A port can be a member of one

untagged, port-based VLAN. All

protocol type. When assigning aother port-based VLAN assignments

for that port must be tagged. port to multiple, protocol-based

VLANs sharing the same type, the

port can be an untagged member

of only one such VLAN.

A port can be a tagged member of

any protocol-based VLAN.

A port can be a tagged member of

any port-based VLAN.

NOTE: A given VLAN must have the same VID on all 802.1Q-compliant

devices in which the VLAN occurs. Also, the ports connecting two 802.1Q

devices should have identical VLAN configurations.

• If all end nodes on a port comply with the 802.1Q standard and are configured to use the

correct VID, you can configure all VLAN assignments on a port as "Tagged" if doing so either

makes it easier to manage your VLAN assignments, or if the authorized, inbound traffic for

all VLANs on the port will be tagged.

Introducing tagged VLAN technology into networks running untagged VLANs 55