RIP Timers

 

Understanding RIP Timers

RIP uses several timers to regulate its operation.

The update interval is the interval at which routes that are learned by RIP are advertised to neighbors. This timer controls the interval between routing updates. The update interval is set to 30 seconds, by default, with a small random amount of time added when the timer is reset. This added time prevents congestion that can occur if all routing devices update their neighbors simultaneously.

To configure the update time interval, include the update-interval statement:

seconds can be a value from 10 through 60.

You can set a route timeout interval. If a route is not refreshed after being installed in the routing table by the specified time interval, the route is marked as invalid and is removed from the routing table after the hold-down period expires.

To configure the route timeout for RIP, include the route-timeout statement:

seconds can be a value from 30 through 360. The default value is 180 seconds.

RIP routes expire when either a route timeout limit is met or a route metric reaches infinity, and the route is no longer valid. However, the expired route is retained in the routing table for a specified period so that neighbors can be notified that the route has been dropped. This time period is set by configuring the hold-down timer. Upon expiration of the hold-down timer, the route is removed from the routing table.

To configure the hold-down timer for RIP, include the holddown statement:

seconds can be a value from 10 through 180. The default value is 120 seconds.

Note

In Junos OS Release 11.1 and later, a retransmission timer is available for RIP demand circuits.

Generally, we recommend against changing the RIP timers, unless the effects of a change are well understood. The route timeout should be at least three times the update interval. Normally, the default values are best left in effect for standard operations.

Example: Configuring RIP Timers

This example shows how to configure the RIP update interval and how to monitor the impact of the change.

Requirements

No special configuration beyond device initialization is required before configuring this example.

Overview

In this example, Device R2 has an update interval of 60 seconds for its neighbor, Device R1, and an update interval of 10 seconds for its neighbor, Device R3.

This example is not necessarily practical, but it is shown for demonstration purposes. Generally, we recommend against changing the RIP timers, unless the effects of a change are well understood. Normally, the default values are best left in effect for standard operations.

An export policy is also shown because an export policy is required as part of the minimum configuration for RIP.

Figure 1 shows the topology used in this example.

Figure 1: RIP Timers Network Topology
RIP Timers Network Topology

CLI Quick Configuration shows the configuration for all of the devices in Figure 1. The section Step-by-Step Procedure describes the steps on Device R2.

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Device R1

Device R2

Device R3

Step-by-Step Procedure

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.

To configure the RIP update interval:

  1. Configure the network interfaces.

    This example shows multiple loopback interface addresses to simulate attached networks.

  2. Configure different update intervals for the two RIP neighbors.

    To configure RIP in Junos OS, you must configure a group that contains the interfaces on which RIP is enabled. You do not need to enable RIP on the loopback interface.

  3. Create the routing policy to advertise both direct and RIP-learned routes.
  4. Apply the routing policy.

    In Junos OS, you can only apply RIP export policies at the group level.

Results

From configuration mode, confirm your configuration by entering the show interfaces, show protocols, and show policy-options commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

If you are done configuring the device, enter commit from configuration mode.

Verification

Confirm that the configuration is working properly.

Checking the RIP Updates Sent by Device R2

Purpose

Make sure that the RIP update packets are sent at the expected interval.

Action

From operational mode, enter the show rip statistics command.

Meaning

The update interval field shows that the interval is 60 seconds for Neighbor R1 and 10 seconds for Neighbor R3. The Updates Sent field shows that Device R2 is sending updates to Device R1 at roughly 1/6 of the rate that it is sending updates to Device R3.

Checking the RIP Updates Received by Device R2

Purpose

Make sure that the RIP update packets are sent at the expected interval.

Action

From operational mode, enter the show rip statistics command.

Meaning

The RIPv2 Updates Received field shows the number of updates received from Device R2.

Checking the RIP Updates Received by Device R3

Purpose

Make sure that the RIP update packets are sent at the expected interval.

Action

From operational mode, enter the show rip statistics command.

Meaning

The RIPv2 Updates Received field shows the number of updates received from Device R2.

Release History Table
Release
Description
In Junos OS Release 11.1 and later, a retransmission timer is available for RIP demand circuits.