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Create a Loopback

Purpose

You can create a physical loopback or configure a local loopback to help diagnose a suspected hardware problem. Creating a physical loopback is recommended because it allows you to test and verify the Channelized DS3 port. If a field engineer is not available to create the physical loopback, you can configure a local loopback for the interface. The local loopback creates a loopback internally in the Physical Interface Card (PIC).

  1. Create a Physical Loopback
  2. Configure a Local Loopback

Create a Physical Loopback

Action

To create a physical loopback at the port, connect the transmit port to the receive port.

Meaning

When you create and test a physical loopback, you are testing the transmit and receive ports of the PIC. This action is recommended if a field engineer is available to create the physical loop as it provides a more complete test of the PIC.


Configure a Local Loopback

Action

To configure a local loopback, follow these steps:

  1. In configuration mode, go to the following hierarchy level, depending on whether you are configuring a full T3 or T1 interface:
    [edit]user@host# edit interfaces interface-name (t3-options | t1-options)
  2. Configure the local loopback:
    [edit interfaces interface-name (t3-options | t1-options] user@host# set loopback local

    The following is an example of the name for a T1 channel on a Channelized DS3 port for a Channelized DS3 to DS1 interface:

    [edit interfaces t1-2/1/1:0 t1-options]
  3. Verify the configuration:
    user@host# show

    For example:

    [edit interfaces t1-2/1/1:0 t1-options]user@host# show loopback local;
  4. Commit the configuration:
    user@host# commit

    For example:

    [edit interfaces t1-2/1/1:0 t1-options]user@host# commit commit complete

Meaning

When you create a local loopback, you create an internal loop on the interface being tested. A local loopback loops the traffic internally on that PIC. A local loopback tests the interconnection of the PIC but does not test the transmit and receive ports.

Note: Remember to delete the loopback statement after completing the test.


Published: 2010-01-29

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