Related Documentation
- M, MX, T Series
- Automatic Protection Switching and Multiplex Section Protection Overview
- Basic Automatic Protect Switching Overview
- Configuring Basic Automatic Protect Switching
- Configuring SONET/SDH Physical Interface Properties
- SONET/SDH Physical Interfaces Configuration Hierarchy
- SONET/SDH Physical Interface Properties Overview
Example: Configuring Basic APS Support on Routers
Requirements for a Basic APS Support
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
Basic APS Overview
Automatic Protection Switching (APS) is used by SONET add/drop multiplexers (ADMs) to protect against circuit failures. The Junos implementation of APS allows you to protect against circuit failures between an ADM and one or more routers, and between multiple interfaces in the same router. When a circuit or router fails, a backup immediately takes over.
To configure APS or MSP, you configure a working and a protect circuit, as shown in Figure 1. To protect against a router failure, you connect two routers to the ADM, configuring one of them as the working router and the second as the protect router. To protect against a PIC or FPC failure, you connect one router to the ADM through both the working and protect circuits, configuring one of the PICs or FPCs as the working circuit and the second as the protect circuit.
Figure 1: APS/MSP Configuration Topologies

![]() | Note: For SDH interfaces, the Junos OS supports multiplex section protection (MSP). You configure MSP with the same CLI statements you use to configure APS. |
Configuring Basic APS Support on Routers
To configure Router A to be the working router and Router B to be the protect router as shown in Figure 1.
- On Router A (the Working Router)
- On Router B (the Protect Circuit)
- On a Single Platform, One Interface as the Working Circuit and Another Interface as the Protect Circuit
On Router A (the Working Router)
Step-by-Step Procedure
Configure basic APS support on Router A as the working router.
- In configuration mode, go to the [edit interfaces interface-name sonet-options] hierarchy level where
the interface is so-6/1/1.[edit]user@host# edit interfaces so-6/1/1 sonet-options
- Configure the working-circuit option as San-Jose[edit interfaces so-6/1/1 sonet-options]user@host# set working-circuit San-Jose
- Configure the authentication-key option as “ $9$B2612345”[edit]user@host# set authentication-key “ $9$B2612345”
On Router B (the Protect Circuit)
Step-by-Step Procedure
Configure basic APS support on Router B as the protect router.
- In configuration mode, go to the [edit interfaces interface-name sonet-options] hierarchy level where
the interface is so-0/0/0.[edit]user@host# edit interfaces so-0/0/0 sonet-options
- Configure the protect-circuit option as San-Jose[edit edit interfaces so-0/0/0 sonet-options]user@host# set protect-circuit San-Jose
- Configure the authentication-key option as “ $9$B2612345” [edit edit interfaces so-0/0/0 sonet-options]user@host# set authentication-key “ $9$B2612345”
- Configure the neighbor option as 192.168.1.2 that is the address of Router A on the
link between A and B.[edit edit interfaces so-0/0/0 sonet-options]user@host# set neighbor 192.168.1.2
On a Single Platform, One Interface as the Working Circuit and Another Interface as the Protect Circuit
Step-by-Step Procedure
Configure one interface as the working circuit.
- In configuration mode, go to the [edit interfaces interface-name sonet-options] hierarchy level where
the interface is so-2/1/1 .[edit]user@host# edit interfaces so-2/1/1 sonet-options
- Configure the working-circuit option as Bayward[edit edit interfaces so-2/1/1 sonet-options]user@host# set protect-circuit Bayward
- Configure the authentication-key option as blarney[edit edit interfaces so-2/1/1 sonet-options]user@host# set authentication-key blarney
Step-by-Step Procedure
Configure one interface as the protect circuit.
- In configuration mode, go to the [edit interfaces interface-name sonet-options] hierarchy level where
the interface is so-3/0/2.[edit]user@host# edit interfaces o-3/0/2 sonet-options
- Configure the working-circuit option as Bayward[edit edit interfaces so-3/0/2 sonet-options]user@host# set protect-circuit Bayward
- Configure the authentication-key option as blarney[edit edit interfaces so-3/0/2 sonet-options]user@host# set authentication-key blarney
Results
Display the results of the configuration:
On Router A (the Working Router)
[edit interfaces so-6/1/1 sonet-options] aps { working-circuit San-Jose; authentication-key “ $9$B2612345” ; }
On Router B (the Protect Circuit)
[edit interfaces so-0/0/0 sonet-options] aps { protect-circuit San-Jose; authentication-key “ $9$B2612345” ; neighbor 192.168.1.2; }
On a Single Platform, One Interface as the Working Circuit and Another Interface as the Protect Circuit
[edit interfaces so-2/1/1 sonet-options] aps { working-circuit bayward; authentication-key blarney; } [edit interfaces so-3/0/2 sonet-options] aps { protect-circuit bayward; authentication-key blarney; }
Related Documentation
- M, MX, T Series
- Automatic Protection Switching and Multiplex Section Protection Overview
- Basic Automatic Protect Switching Overview
- Configuring Basic Automatic Protect Switching
- Configuring SONET/SDH Physical Interface Properties
- SONET/SDH Physical Interfaces Configuration Hierarchy
- SONET/SDH Physical Interface Properties Overview
Published: 2012-12-05
Related Documentation
- M, MX, T Series
- Automatic Protection Switching and Multiplex Section Protection Overview
- Basic Automatic Protect Switching Overview
- Configuring Basic Automatic Protect Switching
- Configuring SONET/SDH Physical Interface Properties
- SONET/SDH Physical Interfaces Configuration Hierarchy
- SONET/SDH Physical Interface Properties Overview