Technical Documentation

Example: Load-Balancing a Network with Aggregated Interfaces


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 1 illustrates the network used in this topic.

Figure 1: Aggregated Interfaces Network Topology

Image g016755.gif

The network topology in Figure 1 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:

Published: 2010-01-30