Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Example: Configuring Multicast-Only Fast Reroute in a PIM Domain

This example shows how to configure multicast-only fast reroute (MoFRR) to minimize packet loss in a network when there is a link failure. It works by enhancing the multicast routing protocol, Protocol Independent Multicast (PIM).

MoFRR transmits a multicast join message from a receiver toward a source on a primary path, while also transmitting a secondary multicast join message from the receiver toward the source on a backup path. Data packets are received from both the primary path and the backup paths. The redundant packets are discarded at topology merge points , based on priority (weights assigned to primary and backup paths). When a failure is detected on the primary path, the repair is made by changing the interface on which packets are accepted to the secondary interface. Because the repair is local, it is fast—greatly improving convergence times in the event of a link failure on the primary path.


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

In this example, only the egress provider edge (PE) router has MoFRR enabled,MoFRR in a PIM domain can be enabled on any of the routers.

MoFRR is supported on MX Series platforms with MPC line cards. As a prerequisite, the router must be set to network-services enhanced-ip mode, and all the line-cards in the platform must be MPCs.

This example requires Junos OS Release 14.1 or later on the egress PE router.


In this example, Device R3 is the egress edge router. MoFRR is enabled on this device only.

OSPF or IS-IS is used for connectivity, though any interior gateway protocol (IGP) or static routes can be used.

PIM sparse mode version 2 is enabled on all devices in the PIM domain. Device R1 serves as the rendezvous point (RP).

Device R3, in addition to MoFRR, also has PIM join load balancing enabled.

For testing purposes, routers are used to simulate the source and the receiver. Device R3 is configured to statically join the desired group by using the set protocols igmp interface fe-1/2/15.0 static group command. It is just joining, not listening. The fe-1/2/15.0 interface is the Device R3 interface facing the receiver. In the case when a real multicast receiver host is not available, as in this example, this static IGMP configuration is useful. On the receiver, to make it listen to the multicast group address, this example uses set protocols sap listen To make the source send multicast traffic, a multicast ping is issued from the source router. The ping command is ping bypass-routing interface fe-1/2/10.0 ttl 10 count 1000000000. The fe-1/2/10.0 interface is the source interface facing Device R1.

MoFRR configuration includes multiple options that are not shown in this example, but are explained separately. The options are as follows:


Figure 1 shows the sample network.

Figure 1: MoFRR in a PIM DomainMoFRR in a PIM Domain

CLI Quick Configuration shows the configuration for all of the devices in Figure 1.

The section Step-by-Step Configuration describes the steps on Device R3.

CLI Quick 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

Device R6

Device Source

Device Receiver

Step-by-Step Configuration


Step-by-Step Procedure

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

To configure Device R3:

  1. Enable enhanced IP mode.

  2. Configure the device interfaces.

  3. For testing purposes only, on the interface facing Device Receiver, simulate IGMP joins.

    If your test environment has receiver hosts, this step is not necessary.

  4. Configure an IGP or static routes.

  5. Configure PIM.

  6. (Optional) Configure PIM join load balancing.

  7. (Optional) Configure per-packet load balancing.

  8. Enable MoFRR.


From configuration mode, confirm your configuration by entering the show chassis, show interfaces, show protocols, show policy-options, and show routing-options 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.


Confirm that the configuration is working properly.

Sending Multicast Traffic Into the PIM Domain


Use a multicast ping command to simulate multicast traffic.



The interface on Device Source, facing Device R1, is fe-1/2/10.0. Keep in mind that multicast pings have a TTL of 1 by default, so you must use the ttl option.

Verifying the Upstream Interfaces


Make sure that the egress device has two upstream interfaces for the multicast group join.



The output shows an active upstream interface and neighbor, and also an MoFRR backup upstream interface and neighbor.

Checking the Multicast Routes


Examine the IP multicast forwarding table to make sure that there is an upstream RPF interface list, with a primary and a backup interface.



The output shows an upstream RPF interface list, with a primary and a backup interface.