Router-on-a-Stick: Inter-VLAN Communication Using a Router. In large and complex networks, the need to segment traffic and divide the network into different segments is crucial. VLANs allow for this logical division of networks to improve security, efficiency, and performance. However, to enable communication between VLANs, we need a method to route traffic between them. This is where the concept of Router-on-a-Stick comes into play. What is Router-on-a-Stick? Router-on-a-Stick is a method for routing between VLANs using a single router interface. In simple terms, instead of having multiple ports on a router for each VLAN, the router uses a single physical port for communication between VLANs. How Does Router-on-a-Stick Work? To set up Router-on-a-Stick, the router needs to be connected to a Trunk Port on a switch that can transmit and receive VLAN Tags. In this configuration: 1.Creating Trunking: The router connects to the switch, and the switch port is specifically configured for carrying multiple VLAN traffic (tagged). 2.Subinterfaces on the Router: Instead of using separate physical ports for each VLAN, the router creates a subinterface for each VLAN. Each subinterface has its own IP address corresponding to the VLAN. 3.VLAN Tagging: The 802.1Q protocol is used to tag the packets so that traffic from each VLAN is properly identified. 4.Routing: After tagging the packets, the router routes them between VLANs. Benefits of Router-on-a-Stick: 1.Resource Efficiency: Instead of needing a physical port for each VLAN, only one physical port is required. 2.Simplified Management: Fewer configurations and complexities for managing network infrastructure. 3.Flexibility: Allows for the creation of multiple VLANs and routing between them using a single router. 4.Cost-effective: Requires less hardware compared to using separate routers for each VLAN. How to Implement Router-on-a-Stick? To implement Router-on-a-Stick, follow these steps: 1.Configure the Trunk Port on the Switch: Change the switch port to trunk mode. Use the 802.1Q protocol for VLAN tagging. 2.Create Subinterfaces on the Router: Create a subinterface for each VLAN on the router. Assign an IP address to each subinterface. Configure the 802.1Q protocol on each subinterface to tag the packets based on VLAN. 3.Connect the Router to the Switch: Connect the router’s trunk port to the switch’s trunk port. 4.Testing and Verifying Configuration: After configuration, use commands like ping to verify communication between VLANs and ensure everything is set up correctly. Challenges and Limitations: 1.Bandwidth Bottleneck: Since only one physical port is used for trunking, the bandwidth of that port might become a limiting factor. 2.Complex Configuration in Large Networks: If there are many VLANs, a large number of subinterfaces need to be created on the router, making it harder to manage and support. | 14 comments on LinkedIn