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. Loop the Entire T3 Interface Towards the Network
2. Create a Loop to the Router from Various Points in the Network

Loop the Entire T3 Interface Towards the Network

Purpose

Creating a loop from the entire T3 interface to the network allows the transport-layer engineer to test the router from various points in the network and isolate the problem..

Note: For a list of interface types associated with the Channelized OC12 IQ interface, see .

Action

To create a loop from the entire T3 interface to the network, follow these steps:

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

   [edit]

   user@host# edit interfaces t3-fpc/pic/port:channel t3-options

2. Configure the loopback:

   [edit interfaces t3-fpc/pic/port:channel t3-options]

   user@host# set loopback remote

3. Verify the configuration:

   user@host# show

   For example:

   [edit interfaces t3-2/1/1:0 t3-options]

   user@host# show

   loopback remote;

4. Commit the configuration:

   user@host# commit

Meaning

The loopback remote 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. 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 7 in Diagnose a Suspected Hardware Problem with a Channelized OC12 or Channelized OC12 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.