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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:

    • ACX5000 Series Routers
    • Junos OS Release 15.1X54–D60

    Overview

    Each working path can be configured using a pseudowire configured through an intermediate PE router (as shown in Figure 1). The protection path provides failure protection for the traffic flowing between the PE routers. Failures are detected through the link down trap.

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

    Topology

    In Figure 1, there are two paths running between Router PE1 and Router PE2. One is the working path between Router PE1 and Router PE2. The other is the protection path between Router PE1 and Router PE3 to Router PE2.

    Figure 1: 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

    Configuration

    The following section describes how to configure Layer 2 circuit connection 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 1 on Router PE1:

    1. Configure the Layer 2 circuit on Router PE1.
      [edit protocols l2circuit]
      user@PE1# set local-switching interface ge-2/0/2.0 connection-protection
      user@PE1# set local-switching interface ge-2/0/2.0 backup-neighbor 192.0.2.2 virtual-circuit-id 2
      user@PE1# set local-switching interface ge-2/0/2.0 backup-neighbor 192.0.2.2 community example
      user@PE1# set local-switching interface ge-2/0/2.0 end-interface interface ge-2/0/1.0
    2. Configure the routing policy on Router PE1.
      [edit policy-options]
      user@PE1# set policy-statement load-balance then load-balance per-packet
      user@PE1# set policy-statement protection-policy term protect from community example
      user@PE1# set policy-statement protection-policy term protect then install-nexthop lsp-regex lsp-protect-*
    3. Configure the routing options on Router PE1.
      [edit routing-options]
      user@PE1# set forwarding-table export load-balance

    Results

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

    user@host> show protocols l2circuit
    local-switching {
    interface ge-2/0/2.0 {
    connection-protection;
    backup-neighbor 192.0.2.2 {
    virtual-circuit-id 2;
    community example;
    }
    end-interface {
    interface ge-2/0/1.0;
    }
    }
    }
    user@host> show policy-options
    policy-statement load-balance {
    then {
    load-balance per-packet;
    }
    }
    policy-statement protection-policy {
    term protect {
    from community example;
    then {
    install-nexthop lsp-regex lsp-protect-*;
    }
    }
    }
    user@host> show routing-options
    forwarding-table {
    export load-balance;
    }

    Modified: 2017-08-31