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Example: Configuring the Transmission Frequency for Link-State PDUs on IS-IS Interfaces

This example shows how to modify the link-state PDU interval time.


Before you begin, configure IS-IS. See Example: Configuring IS-IS for information about the sample IS-IS configuration.


To keep reachability information in the network current, link-state protocols need to originate, distribute, and revoke or time-out topology information. In IS-IS, topology information is encoded in link-state PDUs.

By default, the routing device sends one link-state PDU out an interface every 100 milliseconds. To modify this interval, include the lsp-interval statement:

To disable the transmission of all link-state PDUs, set the interval to 0.

Link-state PDU throttling by use of the lsp-interval statement controls the flooding pace to neighboring routing devices in order to not overload them and also to ensure that user traffic is not delayed on low-bandwidth links.

In this example, an IS-IS routing device on a LAN segment is configured to send link-state PDUs every 1000 milliseconds.

Figure 1 shows the topology used in this example.

Figure 1: IS-IS Link-State PDU Interval TopologyIS-IS Link-State PDU Interval Topology

This example describes the steps on Device R1.



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

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 link-state PDU interval:

  1. Configure the interfaces.

  2. Enable IS-IS on the interfaces.

  3. Modify the link-state PDU interval.

  4. (Optional) Enable tracing for tracking link-state PDU operations.


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

If you are done configuring the device, enter commit from configuration mode. Repeat the configuration on Device R2.


Confirm that the configuration is working properly.

Verifying the Link-State PDU Interval


Check the link-state PDU interval setting on the IS-IS interface.


From operational mode, enter the show isis interface extensive command.


The output shows that the link-state PDU interval is set to 1000 milliseconds.

Checking the Link-State PDU Statistics


Check the number of link-state PDUs sent and received.


From operational mode, enter the show isis statistics command.


The output shows the number of link-state PDUs sent and received on Device R1 and Device R2.

Checking the Trace Log


Check the IS-IS trace log to view the interval between packets.


From operational mode, enter the show log isis-trace | match lsp command.


The output shows that Level 1 and Level 2 link-state PDUs are being sent and received roughly every 1000 milliseconds (1 second).