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Example: Configuring Layer 2 Circuit Switching Protection

 

Unlike Layer 2 circuit protect interfaces (see Example: Configuring Layer 2 Circuit Protect Interfaces), which provide traffic protection for paths configured between the PE routers and CE routers, Layer 2 circuit switching protection provides traffic protection for the paths configured between the PE routers. In the event the path used by a Layer 2 circuit fails, traffic can be switched to an alternate path (or protection path). Switching protection is supported for locally switched Layer 2 circuits and provides 1 to 1 protection for each Layer 2 circuit interface.

When you enable Layer 2 circuit switching protection, each Layer 2 circuit interface requires the following paths:

  • Working path—Used by the Layer 2 circuit when working normally.

  • Protection path—Used by the Layer 2 circuit when the working path fails.

Requirements

This example uses the following hardware and software components:

  • MX Series 5G Universal Routing Platforms

  • Junos OS Release 12.3

Overview

Each working path can be configured to have a either a protection path routed directly to the neighboring PE router (as shown in Figure 1) or indirectly using a pseudowire configured through an intermediate PE router (as shown in Figure 2 and Figure 3). The protection path provides failure protection for the traffic flowing between the PE routers. Ethernet OAM monitors the status of these paths. When OAM detects a failure, it reroutes the traffic from the failed working path to the protection path. You can configure OAM to revert the traffic automatically to the working path when it is restored. You can also manually switch traffic between the working path, the protection path, and back.

Note

Non-stop routing (NSR) and graceful routing engine switchover (GRES) do not support Layer 2 circuit switching protection.

Topology

Figure 1 illustrates Layer 2 circuit local switching. There are two OAM sessions running between Router PE1 and Router PE2. One OAM session is configured over the working path and the other is configured over the protection path.

Figure 1: Connection Protection Enabled Between Router PE1 and Router PE2
Connection Protection Enabled Between
Router PE1 and Router PE2

In Figure 2 and Figure 3, there are two OAM sessions running between Router PE1 and Router PE2. For Figure 2, one OAM session is configured over the working path between Router PE1 and Router PE2. The other OAM session is configured over the protection path between Router PE1 and Router PE3 to Router PE2.

Figure 2: Connection Protection Using a Pseudowire Configured through Router PE3 as the Protection Path
Connection Protection Using a Pseudowire
Configured through Router PE3 as the Protection Path

For Figure 3, one OAM session is configured over the working path, the pseudowire between Router PE1 and Router PE3, then to Router PE2. The other OAM session is configured on the protect path between Router PE1 and Router PE2.

Figure 3: Connection Protection Using a Pseudowire Configured through Router PE3 as the Working Path
Connection Protection Using a Pseudowire
Configured through Router PE3 as the Working Path

Configuration

The following sections describe how to configure each of the variations of Layer 2 circuit connection protection:

Configuring Connection Protection Between Two PE Routers

Step-by-Step Procedure

To configure Layer 2 Circuit switching protection as shown in Figure 1 on Router PE1:

  1. Configure the Layer 2 circuit on Router PE1.
  2. Configure the routing policy on Router PE1.
  3. Enable the routing policy on Router PE1.
  4. Configure OAM on Router PE1. OAM is used to monitor the working path between Router PE1 and Router PE2. In the event of a failure on the working path, traffic is switched automatically to the protection path. A connectivity fault management (CFM) session is configured on the working path and on the protection path. Begin by configuring the OAM maintenance domain.
  5. Configure OAM on Router PE1 for the working path.
  6. Configure OAM on Router PE1 for the protection path.
  7. Configure the OAM maintenance domain on Router PE2.
  8. Configure OAM on Router PE2 for the working path.
  9. Configure OAM on Router PE2 for the protection path.

Results

From configuration mode on Router PE1, confirm your configuration by entering the show protocols l2circuit, show policy-options, show routing-options, and show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

From configuration mode on Router PE2, confirm your configuration by entering the show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verifying that OAM CFM Connections are Active

Purpose

Verify that the CFM connections are active on each of the PE routers.

Action

Execute the following command on each of the PE routers.

  1. Verify that the CFM working connection on Router PE1 is active.

    user@ PE1> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  2. Verify that the CFM protect connection on Router PE1 is active

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection
  3. Verify that the CFM working connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  4. Verify that the CFM protect connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection

Configuring Connection Protection Using Another PE Router for the Protection Path

Step-by-Step Procedure

To configure Layer 2 Circuit switching protection as shown in Figure 2 on Router PE1:

  1. Configure the Layer 2 circuit on Router PE1.
  2. Configure the routing policy on Router PE1.
  3. Configure the routing options on Router PE1.
  4. Configure OAM on Router PE1 to setup the maintenance domain. OAM is used to monitor the working path between Router PE1 and Router PE2. In the event of a failure on the working path, traffic is switched automatically to the protection path.
  5. Configure OAM on Router PE1 for the working path.
  6. Configure OAM on Router PE1 for the protection path.
  7. Configure OAM on Router PE2 to setup the maintenance domain.
  8. Configure OAM on Router PE2 for the working path.
  9. Configure OAM on Router PE2 for the protection path.

Results

From configuration mode on Router PE1, confirm your configuration by entering the show protocols l2circuit, show policy-options, show routing-options, and show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

From configuration mode on Router PE2, confirm your configuration by entering the show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verifying that OAM CFM Connections are Active

Purpose

Verify that the CFM connections are active on each of the PE routers.

Action

Execute the following command on each of the PE routers.

  1. Verify that the CFM working connection on Router PE1 is active.

    user@ PE1> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  2. Verify that the CFM protect connection on Router PE1 is active

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection
  3. Verify that the CFM working connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  4. Verify that the CFM protect connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection

Configuring Connection Protection Using an Another PE Router for the Working Path

Step-by-Step Procedure

To configure Layer 2 Circuit switching protection as shown in Figure 3 on Router PE1:

  1. Configure the Layer 2 circuit on Router PE1.
  2. Configure the policies on Router PE1.
  3. Configure the routing options on Router PE1.
  4. Configure OAM on Router PE1 to setup the maintenance domain. OAM is used to monitor the working path between Router PE1 and Router PE2. In the event of a failure on the working path, traffic is switched automatically to the protection path.
  5. Configure OAM on Router PE1 for the working path.
  6. Configure OAM on Router PE1 for the protection path.
  7. Configure OAM on Router PE2 to setup the maintenance domain.
  8. Configure OAM on Router PE2 for the working path.
  9. Configure OAM on Router PE2 for the protection path.

Results

From configuration mode on Router PE1, confirm your configuration by entering the show protocols l2circuit, show policy-options, show routing-options, and show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

From configuration mode on Router PE2, confirm your configuration by entering the show protocols oam ethernet commands. If the output does not display the intended configuration, repeat the configuration instructions in this example to correct it.

Verifying that OAM CFM Connections are Active

Purpose

Verify that the CFM connections are active on each of the PE routers.

Action

Execute the following command on each of the PE routers.

  1. Verify that the CFM working connection on Router PE1 is active.

    user@ PE1> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  2. Verify that the CFM protect connection on Router PE1 is active

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection
  3. Verify that the CFM working connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association working
  4. Verify that the CFM protect connection on Router PE2 is active.

    user@ PE2> show oam ethernet connectivity-fault-management mep-database maintenance-domain l2circuit-example-md maintenance-association protection