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Example: Configuring Multicast Load Balancing over Aggregated Ethernet Links


This example shows how to configure point-to-multipoint LSPs to load balance across aggregated Ethernet links. The load balancing applies to all traffic types, including multicast. Feature parity for multicast load balancing of point-to-multipoint LSPs over aggregated Ethernet child links on the MX Series routers with MPCs or MICs is supported in Junos OS Releases 11.1R2, 11.2R2, and 11.4.


VPLS multicast load balancing requires Junos OS Release 14.1 or later.


Before you begin:

  1. Configure the router interfaces.

  2. Configure an interior gateway protocol or static routing. See the Junos OS Routing Protocols Library.


This example shows a sample topology and configuration to perform the following tasks:

  • Load balancing VPLS multicast traffic over link aggregation

  • Load balancing point-to-multipoint multicast traffic over link aggregation

  • Re-load balancing after a change in the next-hop topology

    Next-hop topology changes might include but are not limited to:

    • Layer 2 membership change in the link aggregation

    • Indirect next-hop change

    • Composite next-hop change

Load balancing is hash-based, so the higher the number of flows, the better. As is the case with unicast, you can also configure the hash key to be based on Layer 3 and Layer 4 information to achieve a better load-balancing result. There are a few exceptions that are specific to multicast traffic, which might lead to uneven load balancing—for example, when the outgoing interface list includes multiple aggregated interfaces with an unequal number of child links.


For Draft Rosen multicast VPNs (MVPNs), load balancing over aggregated Ethernet interfaces is uneven when the LAGs are all core interfaces. In the case of Next-Generation MBGP MPVNs, multicast traffic is sent over point-to-multipoint and RSVP, and the hash is computed up to the IP headers. In the Draft Rosen case, multicast traffic is tunneled over GRE tunnels, and the hash is used only on GRE tunnel headers. This is why load balancing is not even for Draft Rosen when the LAGs are all core interfaces.

Figure 1 shows the topology for this example. The example includes the configuration for Devices PE1 and PE2.

Figure 1: Multicast Load Balancing over Aggregated Ethernet Links
Multicast Load Balancing over Aggregated Ethernet


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 PE1

Device PE2

Step-by-Step Procedure

To configure Device PE1:

  1. Configure Device PE1 interfaces.

  2. On Device PE1, configure the packet header data to be used for per-flow load balancing.

  3. Configure the routing policy on Device PE1.

  4. Configure Device PE1 routing protocols and MPLS.

  5. Configure VPLS on Device PE1.

Step-by-Step Procedure

To configure Device PE2:

  1. Configure Device PE2 interfaces.

  2. Configure Device PE2 routing protocols and MPLS.

  3. Configure VPLS on Device PE2.


From configuration mode, confirm your configuration by issuing the show forwarding-options, 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.

Device PE1

Device PE2


You can monitor the operation of the routing instance by running the show interfaces ae1.0 extensive and monitor interface traffic commands.

For troubleshooting, you can configure tracing operations for all of the protocols.