Diagnose a Suspected Circuit Problem

Purpose

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 might be located. Figure 10 illustrates a loop from a router to the network.

Figure 10: Loop from the Router to the Network

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 interfaces interface-name (sonet-options | t3-options)

2. Configure the remote loopback:

   [edit interfaces interface-name (sonet-options | 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

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. You can then perform tests to verify the connection from the router to that loopback in the network.

Action

After the transport-layer engineer has created the loop to the router from the network, you must verify the connection from the router to the loopback in the network. Follow Steps 2 through 6 in Diagnose a Suspected Hardware Problem with an ATM1 or ATM2 IQ Interface. 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.