Load Balancing in an MPLS Network > Example: Load-Balancing a Network with Aggregated Interfaces

Purpose

With an aggregated interface, when you configure load balancing using the per-packet statement, the JUNOS software uses the first MPLS label in the hash algorithm to determine the next hop for the LSP. This behavior can result in an uneven distribution of traffic for aggregated interfaces.

This example describes load balancing using an LDP tunneled over RSVP on a network comprised of M-series and T-series routers with aggregated interfaces. Figure 11 illustrates the network used in this section.

Figure 11: Aggregated Interfaces Network Topology

The network topology in Figure 11 illustrates a router-only network with aggregated SONET and Ethernet interfaces that consists of the following components:

• BGP configured on PE routers R0 and R4
• LDP running on R0, R1, R3, and R4
• RSVP running on R1, R2, and R3
• LSPs set up from R1 to R3, and R3 to R1
• Aggregated interfaces on R1, R2, and R3
• The hash key configured on transit router R2
• Load balancing configured on R1

With the hash key configuration on R2, outbound traffic for the aggregated interface varies in terms of Label 1, Label 2, or IP payload. This variance in traffic should result in the equal distribution of traffic across different physical links of the aggregated interface.

The following information is included in this example:

• Verifying the Operation of Load Balancing with Aggregated Interfaces
• For the configuration output of all routers in this network, see Router Configurations for the Aggregated Interfaces Network