Configuring Load Balancing for MPLS LSPs

Load balancing is used to evenly distribute traffic when:

• There are multiple equal-cost next hops over different interfaces to the same destination.
• There is a single next hop over an aggregated interface.

By default, when load balancing is used to help distribute traffic, the JUNOS software employs a hash algorithm to select a next-hop address to install into the forwarding table. Whenever the set of next hops for a destination changes in any way, the next-hop address is reselected by means of the hash algorithm.

You can configure how the hash algorithm is used to load-balance traffic across a set of equal-cost LSPs. The hash algorithm can be configured to use the first MPLS label, the first two MPLS labels, the IP payload, or the first and second MPLS labels and the IP payload. These configurations are described in the following sections:

• Using the First MPLS Label in the Hash Key
• Using the Second MPLS Label in the Hash Key
• Using the IP Payload in the Hash Key
• Using the First Two Labels and the IP Payload in the Hash Key
• Configuring Load Balancing for MPLS LSPs without CSPF

For more information about statements configured under the [edit forwarding-options] hierarchy level, see the JUNOS Policy Framework Configuration Guide.