Example of Networked 802.1Q-compliant devices with multiple VLANs on some ports

In the following network, switches X and Y and servers S1, S2, and the AppleTalk server are 802.1Q-compliant. (Server S3 could also be 802.1Q-compliant, but it makes no difference for this example.) This network includes both protocol-based (AppleTalk) VLANs and port-based VLANs.

  • The VLANs assigned to ports X4 - X6 and Y2 - Y5 can all be untagged because there is only one VLAN assigned per port.

  • Port X1 has two AppleTalk VLANs assigned, which means that one VLAN assigned to this port can be untagged and the other must be tagged.

  • Ports X2 and Y1 have two port-based VLANs assigned, so one can be untagged and the other must be tagged on both ports.

  • Ports X3 and Y6 have two port-based VLANs and one protocol-based VLAN assigned. Thus, one port-based VLAN assigned to this port can be untagged and the other must be tagged. Also, since these two ports share the same link, their VLAN configurations must match.

In the table, "No" means that the port is not a member of that VLAN. For example, port X3 is not a member of the Red VLAN and does not carry Red VLAN traffic. Also, if GVRP were enabled (port-based only), Auto would appear instead of No.

Switch X Switch Y
Port AT-1 VLAN AT-2 VLAN Red VLAN Green VLAN Port AT-1 VLAN AT-2 VLAN Red VLAN Green VLAN
X1 Untagged Tagged No No Y1 No No Untagged Tagged
X2 No No Untagged Tagged Y2 No No No Untagged
X3 No Untagged Untagged Tagged Y3 No Untagged No No
X4 No No No Untagged Y4 No No No Untagged
X5 No No Untagged No Y5 No No Untagged No
X6 Untagged No No No Y6 No Untagged Untagged Tagged
NOTE:

VLAN configurations on ports connected by the same link must match. Because ports X2 and Y5 are opposite ends of the same point-to-point connection, both ports must have the same VLAN configuration, configuring the Red VLAN as "Untagged" and the Green VLAN as "Tagged.”