On Demand Routing (ODR) by Arash Deljoo

On-Demand Routing is not a routing protocol. It uses Cisco Discovery Protocol (CDP) to propagate the IP prefix. ODR is a perfect solution for hub and spoke topology when the spoke routers act as stub routers by connecting to no other router other than the hub. If you only use Cisco routers in your network, running Cisco IOS® 11.2 or later, you can use ODR. If you are running dynamic protocols (for instance, if you are an ISP), ODR is not suitable for your network environment. For more detailed information, refer to Configuring On-Demand Routing.

ODR is fundamentally pertinent in hub and spoke networks and a spoked arrangement where CDP can be utilized. It isn't alluring to include the overhead of a directing convention like RIP, EIGRP, or OSPF. The primary thought is that the prefixes can be traded from the spoke switches (otherwise called stub switches) to the center point switch. The center point switch can publicize a default course to the spoke switches. Prefixes, by means of ODR, can be redistributed into another direction convention to guarantee full start to finish availability with different pieces of the system.

ODR relies on Cisco Discovery Protocol (CDP), so only networks that support CDP can be part of an ODR configuration. This immediately eliminates Frame Relay with point-to-multipoint sub interfaces and other non-broadcast topologies.

ODR is not CPU intensive because it uses CDP, which sends a small packet across Layer 2 every minute. Making the timers more aggressive does not increase CPU usage.