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Using Loopback Testing for Channelized OC12 Interfaces

 

Checklist for Using Loopback Testing for Channelized OC12 and Channelized OC12 IQ Interfaces

Purpose

To use loopback testing to isolate Channelized OC12 and Channelized OC12 IQ interface problems. The naming convention for the Channelized OC12 IQ interface varies depending on the type of interface.

Action

Table 1 provides links and commands for using loopback testing to isolate Channelized OC12 and Channelized OC12 IQ interface problems.

Table 1: Checklist for Using Loopback Testing for Channelized OC12 and Channelized OC12 IQ Interfaces

Tasks

Command or Action

Diagnose a Suspected Hardware Problem with a Channelized OC12 or Channelized OC12 IQ Interface
  1. Create a Loopback

 

Connect the TX port to the RX port.

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

set loopback local

show

commit

  1. Verify That the Interface Is Up

show interfaces t3-fpc/pic/port:channel extensive

  1. Clear Interface Statistics

clear interfaces statistics t3-fpc/pic/port:channel

  1. Force the Link Layer to Stay Up

 

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

set encapsulation cisco-hdlc

show

commit

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

set no-keepalives

show

commit

  1. Verify the Status of the Logical Interface

show interfaces t3-fpc/pic/port:channel

  1. Ping the Channelized Interface

ping interface t3-fpc/pic/port:channel local-IP-address bypass-routing count 1000 rapid

  1. Check for Interface Error Statistics

show interfaces t3-fpc/pic/port:channel extensive

Diagnose a Suspected Circuit Problem
  1. Loop the Entire T3 Interface Toward the Network

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

set loopback remote

show

commit

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

Perform Steps 2 through 8 from Diagnose a Suspected Hardware Problem with a Channelized OC12 or Channelized OC12 IQ Interface.

Diagnose a Suspected Hardware Problem with a Channelized OC12 or Channelized OC12 IQ Interface

Problem

Description: To diagnose a suspected hardware problem with a Channelized OC12 or Channelized OC12 IQ interface, follow these steps:

Solution

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 OC12 or Channelized OC12 IQ 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).

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see the Junos OS Network Interfaces Library for Routing Devices.

  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:

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see the Junos Network Interfaces Configuration Guide.

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

  2. Configure the local loopback:

    The following is an example of the name for a T3 channel on a channelized DS3 interface:

  3. Verify the configuration:

    For example:

  4. Commit the configuration:

    For example:

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.

Verify That the Interface Is Up

Purpose

Display the status of a Channelized OC12 or Channelized OC12 IQ interface to determine whether the physical link is up or down.

Action

To verify that the status of the Channelized OC12 or Channelized OC12 IQ interface is up, use the following Junos OS command-line interface (CLI) operational mode command:

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see Junos Network Interfaces Configuration Guide.

Sample Output

user@host> show interfaces t3-0/3/0:0 extensive

Meaning

The sample output shows that the physical link is up and there are no OC12 alarms or defects. You should not see any OC12 alarms.

Clear Interface Statistics

Purpose

You must reset the Channelized OC12 or Channelized OC12 IQ interface statistics before initiating the ping test. Resetting the statistics provides a clean start so that previous input or output errors and packet statistics do not interfere with the current efforts to diagnose the problem.

Action

To clear all statistics for the interface, use the following Junos OS CLI operational mode command:

Sample Output

user@host> clear interfaces statistics t3-1/1/0:0

Meaning

This command clears the interface statistics counters for the Channelized OC12 interface only.

Note

After a Graceful Routing Engine switchover (GRES) you must run clear interface statistics again or interface statistics will display junk vales.

Force the Link Layer to Stay Up

Purpose

To complete the loopback test, the link layer must remain up. However, Junos OS is designed to recognize that loop connections are not valid connections and to bring the link layer down. You need to force the link layer to stay up by making some configuration changes to the encapsulation and keepalives.

Force the link layer to stay up, follow these steps:

  1. Configure Encapsulation to Cisco-HDLC

  2. Configure No-Keepalives



Configure Encapsulation to Cisco-HDLC

Action

To set the encapsulation on a T3 physical interface, follow these steps:

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

  2. Configure Cisco-HDLC:

  3. Verify the configuration:

    For example:

  4. Commit the change:

    For example:

Meaning

This command sets the interface encapsulation to the Cisco High-level Data-Link Control (HDLC) transport protocol.



Configure No-Keepalives

Action

To disable the sending of link-layer keepalives on a Channelized OC12 or Channelized OC12 IQ interface, follow these steps:

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see Junos Network Interfaces Configuration Guide.

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

  2. Configure no-keepalives:

  3. Verify the configuration:

    For example:

  4. Commit the change:

    For example:

Meaning

By setting no-keepalives, the link layer is forced to stay up. If the setting remains at keepalive, the router will recognize that the same link-layer keepalives are being looped back and will bring the link layer down.

Verify the Status of the Logical Interface

Purpose

To verify the status of the logical interface, use the following Junos OS CLI operational mode command:

Action

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see Junos Network Interfaces Configuration Guide.

Sample Output

user@host> show interfaces t3-0/3/0:11

Meaning

The sample output shows that the channelized interface has the physical and logical links up. There are no alarms or defects.

Ping the Channelized Interface

Purpose

Use the ping command to verify the loopback connection.

Action

To ping the local interface, use the following Junos OS CLI operational mode command:

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see the Junos Network Interfaces Configuration Guide.

Sample Output

user@host> ping interface t3-0/3/0:11 10.0.0.1 bypass-routing count 1000 rapid

Meaning

This command sends 1000 ping packets out of the channelized interface to the local IP address. The ping should complete successfully with no packet loss. If there is any persistent packet loss, open a case with the Juniper Networks Technical Assistance Center (JTAC) at support@juniper.net, or at 1-888-314-JTAC (within the United States) or 1-408-745-9500 (from outside the United States).

Check for Interface Error Statistics

Purpose

Persistent interface error statistics indicate that you need to open a case with JTAC.

Action

To check the local interface for error statistics, use the following Junos OS CLI operational mode command:

Note

For a list of interface types associated with the Channelized OC12 IQ interface, see the Junos Network Interfaces Configuration Guide.

Sample Output

user@host> show interfaces t3-0/3/0:11 extensive

Meaning

Check for any error statistics that may appear in the output. There should not be any input or output errors. If there are any persistent input or output errors, open a case with JTAC at support@juniper.net, or at 1-888-314-JTAC (within the United States) or 1-408-745-9500 (from outside the United States).

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 Toward the Network

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



Loop the Entire T3 Interface Toward 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 the Junos Network Interfaces Configuration Guide.

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:

  2. Configure the loopback:

  3. Verify the configuration:

    For example:

  4. Commit the configuration:

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.