ODR(on demand routing)

ODR ( IOS 12.0.5T ) enables hub and spoke network structure in the hub router automatically to the spoke router ( also known as the stub site ) to provide a default route, stub site routers do not need to run a dynamic routing protocol, no need to configure any static routing, little system resources occupation, can achieve all the local direct subnet to hub router automatic announcement.

ODR on demand routing

In IOS 11.2, Cisco private.

Configuration command: Router ( config router ODR ) # / * this command only need to use the hub

On-demand routing principles:

Static routing is, must manual configuration, at the same time in the network topology changes after the need to manually update; dynamic routing protocols is, they need to occupy the network bandwidth and router resource. In contains hundreds of branch points in the central branch network, using a static route configuration workload will be very large; and the use of dynamic routing protocols will consume large amounts of resources.

In this case, can be used in third ways: ( ODR ). ODR use Cisco discovery protocol ( CDP ) to the branch router router ( distal ) and central transmission between network information. Compared with dynamic routing protocol, ODR provides the IP routing information with very little overhead; and static routing, ODR manual configuration less.

ODR is only fit for the Central Branch topology. In this topology, each branch and the central router adjacent routers only. The branch router also known as distal router. The distal router may be connected to several LAN, but usually only one to the central router WAN connection. The central router needs to learn each branch router connected to the network, while the branch router requires only one point of the central router default route.

Configure the ODR, distal routers using CDP IP prefix information is sent to a central router. The distal router sends all of its direct interconnection network prefix information. Report of the ODR subnet mask, thus support VLSM ( VLSM ).

ODR relies on the CDP in the Central Branch router router and the transfer of information between routers, therefore in the central and branch router between all link must be enabled for the CDP. By default, Cisco router globally enable CDP, and each interface is enabled on the CDP. However, in some WAN link ( such as ATM ), must be explicitly enabled CDP.

The central router will be a point to their default routing to the branch router, and ODR report of the distal network is added to the routing table, the central router configuration, will make these heavy network distributed dynamic routing protocol. The central ODR router will report the branch router's IP address as the next hop address.

ODR is not a routing protocol to exchange information, because it is limited to the IP prefix and default route. ODR does not report the measure, for the ODR reports of all the central router routing, the metric value is set to 1 jump. However, the use of ODR, can be dynamically informed about the stub network routing information, and there is no dynamic routing protocol overhead requirements; at the same time, without manual configuration, can give the distal router provides a default route.

Requirement specification:

In the large-scale routing in a network, for example in a province - - County - the operating point of the composition of the four remote interconnection routing in a network, how to maintain a lot of business router connected subnet routing and configuration of operating point of the static route became a huge burden. This case illustrates how the use of Cisco On-Demand Routing ( ODR ) technology to optimize the routing network an idea.