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.
Connecting multiple VLANs through the same link
