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Example: Configuring BFD for IS-IS

This example describes how to configure the Bidirectional Forwarding Detection (BFD) protocol to detect failures in an IS-IS network.


BFD is not supported with ISIS for IPV6 on QFX10000 series switches.


Before you begin, configure IS-IS on both routers. See Example: Configuring IS-IS for information about the required IS-IS configuration.

This example uses the following hardware and software components:

  • Junos OS Release 7.3 or later

  • M Series, MX Series, and T Series routers


This example shows two routers connected to each other. A loopback interface is configured on each router. IS-IS and BFD protocols are configured on both routers.


Figure 1 shows the sample network.

Figure 1: Configuring BFD for IS-ISConfiguring BFD for IS-IS


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.

Router R1

Router R2


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.


To simply configure BFD for IS-IS, only the minimum-interval statement is required. The BFD protocol selects default parameters for all the other configuration statements when you use the bfd-liveness-detection statement without specifying any parameters.


You can change parameters at any time without stopping or restarting the existing session. BFD automatically adjusts to the new parameter value. However, no changes to BFD parameters take place until the values resynchronize with each BFD peer.

To configure BFD for IS-IS on Routers R1 and R2:

  1. Enable BFD failure detection for IS-IS.

  2. Configure the threshold for the adaptation of the detection time, which must be greater than the multiplier number multiplied by the minimum interval.

  3. Configure the minimum transmit and receive intervals for failure detection.

  4. Configure only the minimum receive interval for failure detection.

  5. Disable BFD adaptation.

  6. Configure the threshold for the transmit interval, which must be greater than the minimum transmit interval.

  7. Configure the minimum transmit interval for failure detection.

  8. Configure the multiplier number, which is the number of hello packets not received by the neighbor that causes the originating interface to be declared down.

  9. Configure the BFD version used for detection.

    The default is to have the version detected automatically.


From configuration mode, confirm your configuration by issuing the show protocols isis interface command. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.


Confirm that the configuration is working properly.

Verifying the Connection Between Routers R1 and R2


Make sure that Routers R1 and R2 are connected to each other.


Ping the other router to check the connectivity between the two routers as per the network topology.


Routers R1 and R2 are connected to each other.

Verifying That IS-IS Is Configured


Make sure that the IS-IS instance is running on both routers.


Use the show isis database statement to check if the IS-IS instance is running on both routers, R1 and R2.


IS-IS is configured on both routers, R1 and R2.

Verifying That BFD Is configured


Make sure that the BFD instance is running on both routers, R1 and R2.


Use the show bfd session detail statement to check if BFD instance is running on the routers.


BFD is configured on Routers R1 and R2 for detecting failures in the IS-IS network.