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Configuring On-Demand Routing
IPC-196
Cisco IOS IP Configuration Guide
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:
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.
Command Purpose
Router(config)# router odr
Enables ODR on the hub router.