The Routing Interface

Routing interfaces are configured by entering the interface command from the configuration command mode, specifying the interface ID and whether the interface is a VLAN or a loopback interface. If the interface has not previously been created, this command creates a new routing interface.

A VLAN routing interface can be configured before its VLAN is created in system configuration mode, but VLANs must be created from the system CLI before they will be operational within IP routing. See Configuring VLANs for VLAN configuration details.

Each VLAN or loopback interface must be configured for routing separately using the interface command. To end configuration on one interface before configuring another, type exit at the command prompt. Enabling the interface for IP routing is required using the no shutdown command before exiting the interface mode.

IPv4 forwarding is enabled by default on a routing interface. Use the no ip forwarding command within interface configuration command mode to disable IPv4 forwarding on a routing interface.

IPv6 forwarding is disabled by default on a routing interface.

Note

IPv4 and IPv6 forwarding are both enabled by default on loopback interfaces. Without forwarding, a loopback interface is unreachable. This configuration setting cannot be modified.