On-Demand Routing Commands

Use the commands in this chapter to configure On-Demand Routing (ODR). For ODR configuration information and examples, refer to the "Configuring On-Demand Routing" chapter of the Cisco IOS IP and IP Routing Configuration Guide.

router odr

To configure a router to accept On-Demand Routing (ODR) routes from a stub routers, use the router odr global configuration command. To disable ODR, use the no form of this command.

router odr

no router odr

Syntax Description

There are no arguments or keywords for this command.

Defaults

The router ignores any received ODR information.

Command Modes

Global configuration

Command History

Release Modification

11.2

This command was introduced.

Release	Modification
11.2	This command was introduced.

Usage Guidelines

Use this command on hub routers to enable ODR to update the routing table with information learned via ODR stub routers.

Examples

The following example sets up the routers in the distribution list to accept ODR routes from the specified access list:

router odr
 distribute-list 101 in
access-list 101 permit ip host 10.0.0.1 198.92.110.0 255.255.255.0
access-list 101 permit ip 11.1.1.1 255.0.0.0 198.92.111.0 255.255.255.0
router ospf 1
 redistribute odr subnets

Related Commands

Command Description

distance (IP)

Defines an administrative distance.

distribute-list in (IP)

Filters networks received in updates.

distribute-list out (IP)

Suppresses networks from being advertised in updates.

maximum-paths

Controls the maximum number of parallel routes an IP routing protocol can support.

Command	Description
distance (IP)	Defines an administrative distance.
distribute-list in (IP)	Filters networks received in updates.
distribute-list out (IP)	Suppresses networks from being advertised in updates.
maximum-paths	Controls the maximum number of parallel routes an IP routing protocol can support.

timers basic (ODR)

To adjust ODR network timers, use the timers basic router configuration command. To restore the default timers, use the no form of this command.

timers basic update invalid holddown flush [sleeptime]

no timers basic

Syntax Description

update

Rate in seconds at which updates are sent. This is the fundamental timing parameter of the routing protocol.

invalid

Interval of time in seconds after which a route is declared invalid; it should be at least three times the value of the updateargument. A route becomes invalid when there is an absence of updates that refresh the route. The route then enters holddown. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets.

holddown

Interval in seconds during which routing information regarding better paths is suppressed. It should be at least three times the value of the update argument. A route enters into a holddown state when an update packet is received that indicates the route is unreachable. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets. When holddown expires, routes advertised by other sources are accepted and the route is no longer inaccessible.

flush

Amount of time in seconds that must pass before the route is removed from the routing table; the interval specified must be at least the sum of the invalid and holddown arguments. If it is less than this sum, the proper holddown interval cannot elapse, which results in a new route being accepted before the holddown interval expires.

sleeptime

(Optional) Interval in milliseconds for postponing routing updates in the event of a flash update. The the sleeptime value should be less than the update time. If the sleeptime is greater than the update time, routing tables will become unsynchronized.

update	Rate in seconds at which updates are sent. This is the fundamental timing parameter of the routing protocol.
invalid	Interval of time in seconds after which a route is declared invalid; it should be at least three times the value of the updateargument. A route becomes invalid when there is an absence of updates that refresh the route. The route then enters holddown. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets.
holddown	Interval in seconds during which routing information regarding better paths is suppressed. It should be at least three times the value of the update argument. A route enters into a holddown state when an update packet is received that indicates the route is unreachable. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets. When holddown expires, routes advertised by other sources are accepted and the route is no longer inaccessible.
flush	Amount of time in seconds that must pass before the route is removed from the routing table; the interval specified must be at least the sum of the invalid and holddown arguments. If it is less than this sum, the proper holddown interval cannot elapse, which results in a new route being accepted before the holddown interval expires.
sleeptime	(Optional) Interval in milliseconds for postponing routing updates in the event of a flash update. The the sleeptime value should be less than the update time. If the sleeptime is greater than the update time, routing tables will become unsynchronized.

Defaults

update is 90 seconds.

invalid is 270 seconds.

holddown is 280 seconds.

flush is 630 seconds.

sleeptime is 0 milliseconds.

Command Modes

Router configuration

Command History

Release Modification

10.0

This command was introduced.

Release	Modification
10.0	This command was introduced.

Usage Guidelines

The basic timing parameters for ODR are adjustable. Because this routing protocol is executing a distributed, asynchronous routing algorithm, it is important that these timers be the same for all routers and access servers in the network.

Note The current and default timer values can be seen by inspecting the output of the show ip protocols EXEC command. The relationships of the various timers should be preserved as described previously.

Examples

The following example sets updates to be broadcast every 5 seconds. If a router is not heard from in 15 seconds, the route is declared unusable. Further information is suppressed for an additional 15 seconds. At the end of the suppression period, the route is flushed from the routing table.

router odr 109
 timers basic 5  15  15  30

Note that by setting a short update period, you run the risk of congesting slow-speed serial lines; however, this is not a big concern on faster-speed Ethernets and T1-rate serial lines. Also, if you have many routes in your updates, you can cause the routers to spend an excessive amount of time processing updates.

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