Diagnose a Suspected Circuit Problem

When you suspect a circuit problem, it is important to work with the transport-layer engineer to resolve the problem. The transport-layer engineer may ask you to create a loop from the router to the network, or the engineer may create a loop to the router from various points in the network.

To diagnose a suspected circuit problem, follow these steps:

1. Create a Loop from the Router to the Network
2. Create a Loop to the Router from Various Points in the Network

Create a Loop from the Router to the Network

Purpose

Creating a loop from the router to the network allows the transport-layer engineer to test the router from various points in the network. This helps the engineer isolate where the problem is located.

Action

To create a loop from the router to the network, follow these steps:

1. In configuration mode, go to the following hierarchy level:

   [edit]

   user@host# edit interface interface-name t3-options

2. Configure the remote loopback:

   [edit interfaces interface-name t3-options]

   user@host# set loopback remote

3. Verify the configuration:

   user@host# show

   For example:

   [edit interfaces t3-1/0/0 t3-options]

   user@host# show

   loopback remote;

4. Commit the change:

   user@host# commit

   For example:

   [edit interfaces t3-1/0/0 t3-options]

   user@host# commit

   commit complete

Meaning

This command loops any traffic from the network back into the network.

Create a Loop to the Router from Various Points in the Network

Purpose

The transport-layer engineer creates a loop to the router from various points in the network so that you can then perform tests to verify the connection from the router to that loopback in the network.

Action

To verify the connection from the router to a loopback in the network, follow Steps 2 through 8 in .

Keep in mind that any problems encountered in the test indicate a problem with the connection from the router to the loopback in the network. By performing tests to loopbacks at various points in the network, you can isolate the source of the problem.