Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

ON THIS PAGE

Example: Configuring APS Load Sharing Between Circuit Pairs

 

Requirements for APS Load Sharing Between Circuit Pairs

This example uses the following hardware and software components:

  • Two MX Series, M Series, or T Series routers.

  • Junos OS Release 7.4 or later

Overview

When two routers are connected to a single add/drop multiplexer (ADM), you can have them back up each other on two different pairs of circuits. This arrangement provides load balancing between the routers if one of the working circuits fails.

Figure 1 illustrates load sharing between circuits on two routers. Router A has a working circuit “Start” and a protect circuit “Up,” and Router B has a working circuit “Up” and a protect circuit “Start.” Under normal circumstances, Router A carries the “Start” circuit traffic and Router B carries the “Up” circuit traffic. If the working circuit “Start” were to fail, Router B would end up carrying all the traffic for both the “Start” and “Up” circuits.

To balance the load between the circuits, you pair the two circuits. In this case, you pair the “Start” and “Up” circuits. Then, if the working circuit “Start” fails, the two routers automatically switch the “Up” traffic from the working to the protect circuit so that each router is still carrying only one circuit’s worth of traffic. That is, the working circuit on Router A would be “Up” and the working circuit on Router B would be “Start.”

Topology

Figure 1: APS Load Sharing Between Circuit Pairs
APS Load Sharing Between Circuit Pairs

Configuring APS Load Sharing Between Circuit Pairs

To configure APS load sharing to match the configuration shown in Figure 1, perform the following tasks:

Configuring APS Load Sharing on Router A

Step-by-Step Procedure

Perform the following steps on the first interface—that is, on the so-7/0/0 interface:

  1. Configure the working circuit as start.
  2. Configure the authentication key as linsey.
  3. Configure the paired group as Router A-Router B.

    Configure the other options as needed.

Step-by-Step Procedure

Perform the following steps on the other interface—on the so-0/0/0 interface:

  1. Configure the protect circuit as up.
  2. Configure the authentication key as woolsey.
  3. Configure the paired group as Router A-Router B.

    Configure the other options as needed.

Configuring APS Load Sharing on Router B

Step-by-Step Procedure

Perform the following steps on the first interface—that is, on the so-1/0/0 interface:

  1. Configure the working circuit as up.
  2. Configure the authentication key as woolsey.
  3. Configure the paired group as Router A-Router B.

    Configure the other options as needed.

Step-by-Step Procedure

Perform the following steps on the other interface—that is, on the so-6/0/0 interface:

  1. Configure the protect circuit as start.
  2. Configure the authentication key as linsey.
  3. Configure the paired group as Router A-Router B.

    Configure the other options as needed.

Related Documentation