What is inter-VLAN routing and what common devices implement it?

• A. Inter-VLAN routing enables traffic between VLANs using a router or a Layer 3 switch.
• B. Inter-VLAN routing is used to connect VLANs on the same switch without a router.
• C. Inter-VLAN routing duplicates VLAN traffic in a single broadcast domain.
• D. Inter-VLAN routing is performed by the physical layer only.

Answer: (A)

Inter-VLAN routing is about moving traffic between devices on different VLANs by routing between their IP subnets. VLANs segment the network into separate broadcast domains, so a switch that only forwards within a VLAN cannot by itself send a frame from one VLAN to another. To allow communication across VLANs you need a device that can route: a router or a Layer 3 (multilayer) switch. In practice, a Layer 3 switch uses switch virtual interfaces for each VLAN and enables routing between them, while a traditional router can handle this with subinterfaces on a single trunk (router-on-a-stick), each subinterface associated with a different VLAN. That’s why the correct description is that inter-VLAN routing enables traffic between VLANs using a router or a Layer 3 switch. The other statements don’t fit because inter-VLAN routing requires routing functionality, VLANs remain separate broadcast domains unless you route between them, and routing is not a purely physical-layer operation.