8.5 On Demand Routing
8.5.2 Configuring ODR
ODR is enabled with a single command, router odr. No networks or other parameters must be specified. CDP is enabled by default; it needs to be enabled only if it has been turned off for some reason. The command to enable the CDP process on a router is cdp run. To enable CDP on a specific interface, the command is cdp enable.

The Figure shows a typical hub-and-spoke topology. To configure ODR, the hub router will have the router odr command. As long as all routers are running IOS 11.2 or later and the connecting medium supports SNAP (such as the Frame Relay shown), ODR is operational and the hub will learn the stub networks. The only configuration necessary at the stub routers is a static default route to the hub router.

ODR can also be redistributed into routing protocols. If the Baghdad router in the graphic needed to advertise the ODR-discovered routes into OSPF, Baghdad's configuration could be:

Router odr
!
router ospf 1
redistribute odr metric 100
network 172.16.0.0 0.0.255.255 area 1

Lab Activity    
  You have been contracted by a small bank to install a Frame Relay network to connect their offices in Atlanta and Houston. The frame relay cloud may grow at a later date and to avoid the headache of numerous static routes on the Atlanta hub router, you decide to configure ODR. You have ordered Frame Relay service from a national Frame Relay service provider and have received the DLCIs in the above diagram. Routing should be handled using IGRP. Lastly, the ODR information needs to be redistributed into IGRP.