Cisco Systems 78-11741-02 manual On-Demand Routing Configuration Task List, Enabling ODR, IPC-196

Configuring On-Demand Routing

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the “Identifying Supported Platforms” section in the “Using Cisco IOS Software” chapter in this book.

On-Demand Routing Configuration Task List

To configure ODR, perform the tasks described in the following sections. The tasks in the first section are required; the tasks in the remaining sections are optional:

•Enabling ODR (Required)

•Filtering ODR Information (Optional)

•Redistributing ODR Information into the Dynamic Routing Protocol of the Hub (Optional)

•Reconfiguring CDP or ODR Timers (Optional)

•Using ODR with Dialer Mappings (Optional)

Enabling ODR

ODR allows you to easily install IP stub networks where the hubs dynamically maintain routes to the stub networks. This installation is accomplished without requiring the configuration of an IP routing protocol on the stubs.

On stub routers that support the ODR feature, the stub router advertises IP prefixes corresponding to the IP networks configured on all directly connected interfaces. If the interface has multiple logical IP networks configured, only the primary IP network is advertised through ODR. Because ODR advertises IP prefixes and not simply IP network numbers, ODR is able to carry variable-length subnet mask (VSLM) information.

To enable ODR, use the following command in global configuration mode:

Command	Purpose
Router(config)# router odr	Enables ODR on the hub router.

Once ODR is enabled on a hub router, the hub router begins installing stub network routes in the IP forwarding table. The hub router also can be configured to redistribute these routes into any configured dynamic IP routing protocols.

On the stub router, no IP routing protocol must be configured. In fact, from the standpoint of ODR, a router is automatically considered to be a stub when no IP routing protocols have been configured.

ODR uses the Cisco Discovery Protocol (CDP) to carry minimal routing information between the hub and stub routers. The stub routers send IP prefixes to the hub router. The hub router provides default route information to the stub routers, thereby eliminating the need to configure a default route on each stub router.

Using the no cdp run global configuration command disables the propagation of ODR stub routing information entirely. Using the no cdp enable interface configuration command disables the propagation of ODR information on a particular interface.

Cisco IOS IP Configuration Guide

IPC-196