Routing between VLANs using virtual routing interfaces (Layer 3 Switches only)

RUCKUS Layer 3 Switches offer the ability to create a virtual routing interface within a Layer 2 STP port-based VLAN. This combination of multiple Layer 2 or Layer 3 broadcast domains, or both, and virtual routing interfaces are the basis for Ruckus Networks’ very powerful Integrated Switch Routing (ISR) technology. ISR is very flexible and can solve many networking problems. The following example is meant to provide ideas by demonstrating some of the concepts of ISR.

Suppose you want to move routing out to each of three buildings in a network. Remember that the only protocols present on VLAN 2 and VLAN 3 are IP. Therefore, you can eliminate tagged ports 1/1/25 and 1/1/26 from both VLAN 2 and VLAN 3 and create new tagged port-based VLANs to support separate IP subnets for each backbone link.

You also need to create unique IP subnets within VLAN 2 and VLAN 3 at each building. This will create a fully routed IP backbone for VLAN 2 and VLAN 3. However, VLAN 4 has no protocol restrictions across the backbone. In fact there are requirements for NetBIOS and DecNet to be bridged among the three building locations. The IP subnet that exists within VLAN 4 must remain a flat Layer 2 switched STP domain. You enable routing for IP on a virtual routing interface only on Device-A. This will provide the flat IP segment with connectivity to the rest of the network. Within VLAN 4 IP will follow the STP topology. All other IP subnets will be fully routed and have use of all paths at all times during normal operation.

The following figure shows the configuration described above.

Figure 1. Routing between protocol-based VLANs

To configure the Layer 3 VLANs and virtual routing interfaces on the Layer 3 Switch in the above figure, use the following procedure.