Overlapping (Tagged) VLANs

A port can be a member of more than one VLAN of the same type if the device to which the port connects complies with the 802.1Q VLAN standard.

For example, a port connected to a central server using a network interface card (NIC) that complies with the 802.1Q standard can be a member of multiple VLANs, allowing members of multiple VLANs to use the server.
  • Although these VLANs cannot communicate with each other through the server, they can all access the server over the same connection from the switch.

  • Where VLANs overlap in this way, VLAN "tags" are used in the individual packets to distinguish between traffic from different VLANs.

  • A VLAN tag includes the particular VLAN I.D. (VID) of the VLAN on which the packet was generated.

Overlapping VLANs using the same server

Similarly, using 802.1Q-compliant switches, you can connect multiple VLANs through a single switch-to-switch link.