Load Balancing in an MPLS Network

In an Multiprotocol Label Switched (MPLS) network, load balancing is the process of distributing traffic equally across lable switched paths. When you have added several LSPs to the same egress router, the default behavior of the JUNOS software is to select the LSP with the lowest metric to carry all traffic. If all of the LSPs have the same metric, one of the LSPs is selected at random and all traffic is forwarded over it. You can change this default behavior by configuring load balancing on an ingress router, allowing the JUNOS software to distribute the traffic equally across LSPs. (See Table 8.)

The terms node and router are used interchangeably throughout this book.

Table 8: Checklist for Load Balancing in an MPLS Network

Load Balancing in an MPLS Network Tasks	Command or Action
Load Balancing Overview
Load-Balancing Options	The following load-balancing options are included: IPv4 address family (INET) in the hash key MPLS labels and IP payload in the hash key LSP bandwidth
Configuring and Verifying Load Balancing
Define a Load-Balancing Policy	[edit] edit policy-options [edit policy-options] set policy-statement policy-name then load-balance      per-packet show commit
Apply the Load-Balancing Policy to the Forwarding Table	[edit] edit routing-options [edit routing-options] set forwarding-table export policy-name show commit
Verify That Load Balancing Is Working	show configuration show route show route forwarding-table show mpls lsp statistics monitor interface traffic clear mpls lsp statistics clear interface statistics
Example: Load-Balanced MPLS Network
Router Configurations for the Load-Balanced MPLS Network	show configuration | no-more
Using Hash-Key Load Balancing for LSP Traffic
Configuring MPLS Labels and IP Payload to Load-Balance LSP Traffic	[edit] edit forwarding-options hash-key [edit forwarding-options hash-key] set family mpls label-1 set family mpls label-2 set family mpls payload ip show commit
Configuring the IPv4 Address Family to Load-Balance LSP Traffic	[edit] edit forwarding-options hash-key [edit forwarding-options hash-key] set family inet layer-3 set family inet layer-4 show commit
Hash Key Network Examples
Example: Load-Balancing a Network with Aggregated Interfaces
Verifying the Operation of Load Balancing with Aggregated Interfaces	show configuration forwarding-options show interfaces statistics interface-name detail show mpls lsp statistics
Router Configurations for the Aggregated Interfaces Network	show configuration | no-more
Example: Load-Balancing a Network Using INET in the Hash Key
Verifying the Operation of INET Load Balancing	show configuration show route forwarding-table destination destination show route monitor interface traffic show mpls lsp statistics
Router Configurations for the INET Load-Balanced Network	show configuration | no-more
Using Bandwidth to Unevenly Load-Balance RSVP LSPs
Configure Bandwidth to Unevenly Load-Balance Traffic	[edit] edit protocols mpls [edit protocols mpls] set label-switched-path lsp-path-name bandwidth bps show [edit protocols rsvp] set load-balance bandwidth show commit
Verify the Operation of Uneven Bandwidth Load Balancing	show route protocol rsvp detail show mpls lsp statistics
Router Configurations for Bandwidth Load Balancing	show configuration | no-more
Traffic Flows Before Load Balancing	show route | find mpls monitor interface traffic show mpls lsp statistics