VLAN routing works by allowing communication between different VLANs (Virtual Local Area Networks) within a network infrastructure. VLANs logically segment a physical network into multiple virtual networks, each with its own broadcast domain. When VLAN routing is implemented, a device such as a Layer 3 switch or a router with VLAN support is used to facilitate communication between VLANs. This device routes traffic between VLANs based on Layer 3 (IP) addresses, effectively enabling inter-VLAN communication while maintaining the isolation provided by VLAN segmentation.
Routing between VLANs involves the process of forwarding data packets between different VLANs within a network. This typically requires a router or a Layer 3 switch capable of routing between VLANs. When a device in one VLAN needs to communicate with a device in another VLAN, the traffic is sent to the router or Layer 3 switch. The router examines the destination IP address of the packet and uses its routing table to determine the best path to forward the packet to the destination VLAN. This process allows devices in different VLANs to communicate as if they were on the same physical network.
A VLAN router, also known as a Layer 3 switch or a VLAN-aware router, is a networking device that supports routing between VLANs. Unlike traditional routers that operate primarily at Layer 3 of the OSI model, VLAN routers are specifically designed to handle inter-VLAN routing. They maintain routing tables that map VLANs to IP subnets and determine how traffic should be forwarded between VLANs based on IP addresses. VLAN routers facilitate efficient communication between different VLANs while maintaining the security and segmentation benefits of VLANs.
There are primarily two methods of VLAN routing: router-on-a-stick and Layer 3 switch routing. Router-on-a-stick involves using a single physical interface on a router to route traffic between multiple VLANs by tagging packets with VLAN identifiers (802.1Q tags). The router then processes these tagged packets and routes them between VLANs based on their VLAN tags and IP addresses. Layer 3 switch routing, on the other hand, uses a Layer 3 switch that has built-in routing capabilities. This switch can route traffic between VLANs directly within the switch hardware, offering faster and more efficient inter-VLAN communication compared to traditional router-on-a-stick configurations.
VLAN routing operates at Layer 3 (Network layer) of the OSI model. While VLANs themselves are a Layer 2 (Data Link layer) concept, VLAN routing involves forwarding traffic based on IP addresses, which is a function of Layer 3. Therefore, VLAN routing is considered a Layer 3 activity because it requires devices like routers or Layer 3 switches to interpret IP addresses and make routing decisions between VLANs based on these addresses.