You can think of VLANs as segmenting a switch into multiple networks. Each port could belong to a different VLAN. Contrary to what some believe, VLANs should not be a security mechanism. The bridge table can be flooded and switch can start to act like a hub, breaking the VLAN broadcast segmentation.
A router is required if an ARP request goes unanswered. That means the host is not on your local network. So in order to connect multiple VLANs:
- You can connect a port from each VLAN to a router and set up the routes.
- You can use virtual interfaces in each VLAN. Layer 3 switches.
- With 802.1q you can tag frames with VLAN identifiers. This enables you to connect multiple switches to the same VLAN.
- Tag Protocol Identifier (TPID)
- Tag Control Information (TCI)
- Truck ports