VLAN Routing Configuration
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VLAN Routing
You can configure the Unified Switch with some ports supporting VLANs and some
supporting routing. You can also configure the Unified Switch to allow traffic on a VLAN to
be treated as if the VLAN were a router port.
When a port is enabled for bridging (default) rather than routing, all normal bridge processing
is performed for an inbound packet, which is then associated with a VLAN. Its MAC
Destination Address (MAC DA) and VLAN ID are used to search the MAC address table. If
routing is enabled for the VLAN and the MAC DA of an inbound unicast packet is that of the
internal bridge-router interface, the packet will be routed. An inbound multicast packet will be
forwarded to all ports in the VLAN, plus the internal bridge-router interface if it was received
on a routed VLAN.
Since a port can be configured to belong to more than one VLAN, VLAN routing might be
enabled for all of the VLANs on the port, or for a subset. VLAN Routing can be used to allow
more than one physical port to reside on the same subnet. It could also be used when a VLAN
spans multiple physical networks, or when additional segmentation or security is required.
This section shows how to configure the Unified Switch to support VLAN routing. A port can
be either a VLAN port or a router port, but not both. However, a VLAN port may be part of a
VLAN that is itself a router port.
VLAN Routing Configuration
This section provides an example of how to configure the Unified Switch to support VLAN
routing. The configuration of the VLAN router port is similar to that of a physical port. The
main difference is that, after the VLAN has been created, you must use the
show ip vlan
command to determine the VLAN’s interface ID so that you can use it in the router
configuration commands.
CLI Examples
The diagram in this section shows a Unified Switch configured for VLAN routing. It connects
two VLANs, with two ports participating in one VLAN, and one port in the other. The script
shows the commands you would use to configure the Unified Switch to provide the VLAN
routing support shown in the diagram.
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