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Table Of Contents
Triggered Extensions to RIP
Feature Summary
Triggered extensions to IP RIP increase efficiency of RIP on point-to-point, serial interfaces.
Routers are used on connection-oriented networks to allow potential connectivity to many remote destinations. Circuits on the WAN are established on demand and are relinquished when the traffic subsides. Depending on the application, the connection between any two sites for user data could be short and relatively infrequent.
There were two problems using RIP to connect to a WAN:
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Periodic broadcasting by RIP generally prevented WAN circuits from being closed.
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To overcome these limitations, triggered extensions to RIP cause RIP to send information on the WAN only when there has been an update to the routing database. Periodic update packets are suppressed over the interface on which this feature is enabled.
Benefit
RIP routing traffic is reduced on point-to-point, serial interfaces. Therefore, you can save money on an on-demand circuit for which you are charged for usage.
Platforms
This feature is supported on all platforms running Cisco IOS Release 12.0(1)T that include RIP.
Prerequisites
RIP must be enabled for this feature to function. This feature runs on a point-to-point, serial interface only.
Supported RFCs
This feature partially supports RFC 2091, Triggered Extensions to RIP to Support Demand Circuits.
Configuration Tasks
To enable triggered extensions to RIP, use the following commands beginning in global configuration mode:
interface serial number
Configure a serial interface.
ip rip triggered
Enable triggered extensions to RIP.
To display the contents of the RIP private database, use the following command in EXEC mode:
show ip rip database [prefix mask]
Display the contents of the RIP private database.
Command Reference
This section documents the following new commands. All other commands used in this feature module can be found in the Cisco IOS 12.0 documentation set.
ip rip triggered
To enable triggered extensions of RIP, use the ip rip triggered interface configuration command. To disable triggered extensions to RIP, use the no form of this command.
ip rip triggered
Syntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 12.0(1)T.
When triggered extensions to RIP are enabled, routing updates are transmitted on the WAN only if one of the following occurs:
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You might want to enable this feature if you are using an on-demand circuit and you are charged for usage time. Fewer routing updates will incur lower usage costs.
Entries in the routing database can be either temporary or semi-permanent. Entries learned from broadcasts on LANs are temporary; they will expire if not periodically refreshed by more broadcasts.
Entries learned from a triggered response on the WAN are semi-permanent; they do not time out like other entries. Certain events can cause these routes to time out, such as the interface going down, or if the outgoing interface is the same as the incoming interface. Neighbor updates of the routes with a metric of 16 (infinity) mean the route is unreachable, and those routes are eventually removed from the routing table.
Example
The following example enables triggered extensions to RIP:
interface serial 0ip rip triggeredRelated Commands
show ip rip database
To display the contents of the RIP private database when triggered extensions to RIP are enabled, use the show ip rip database EXEC command.
show ip rip database [prefix mask]
Syntax Description
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 12.0(1)T.
The RIP private database is populated only if triggered extensions to RIP are enabled with the ip rip triggered command.
Sample Displays
The following is sample output of the show ip rip database command:
Router# show ip rip database172.19.0.0/16 auto-summary172.19.64.0/24 directly connected, Ethernet0172.19.65.0/24[1] via 172.19.70.36, 00:00:17, Serial1[2] via 172.19.67.38, 00:00:25, Serial0172.19.67.0/24 directly connected, Serial0172.19.67.38/32 directly connected, Serial0172.19.70.0/24 directly connected, Serial1172.19.86.0/24[1] via 172.19.67.38, 00:00:25, Serial0[1] via 172.19.70.36, 00:00:17, Serial1The following is sample output of the show ip rip database command with a prefix and mask:
Router# show ip rip database 172.19.86.0 255.255.255.0172.19.86.0/24[1] via 172.19.67.38, 00:00:25, Serial0[1] via 172.19.70.36, 00:00:14, Serial1describes the fields in the first display.
Related Commands