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Troubleshooting Interfaces

This topic discusses various troubleshooting scenarios.

Troubleshooting: Management Interface Link Is Down for Junos OS Evolved

Problem

Description

The Ethernet Link Down alarm is raised when you run the show chassis alarm operational mode command on the following devices:

  • ACX routers (ACX7100-32C, ACX7100-48L)

  • PTX routers (PTX10001-36MR, PTX10003, PTX10004, PTX10008)

  • QFX switches (QFX5130-32CD, QFX5220-32CD, QFX5220-128C)

Diagnosis

Perform the following tests to check if the management interface is down on the primary Routing Engine or the backup Routing Engine:

  1. Run the show chassis alarms command.

    show chassis alarms

    Is the alarm Ethernet Link Down displayed against the management interface of the primary Routing Engine (Host 0)?

    • Yes: Contact Juniper Networks Technical Assistance Center (JTAC) for further assistance.

    • No: Continue to the next diagnostic test.

  1. Run the show interfaces re0:mgmt-0 and the show interfaces re0:mgmt-0 terse operational mode commands.

    show interfaces re0:mgmt-0

    show interfaces re0:mgmt-0 terse

    Is the management interface on the primary Routing Engine up?

    • Yes: Continue to resolution.

    • No: Contact JTAC for further assistance.

Resolution

To Resolve This Issue

The chassis alarm was raised for the management interface in the backup Routing Engine (Host 1) and not for the primary Routing Engine (Host 0).

Implement one of the following solutions on the backup Routing Engine to resolve this issue:

  • Disable the management interface in the backup Routing Engine:

    1. In configuration mode, go to the [edit groups re1] hierarchy level.

    2. Disable the re1:mgmt-0 interface.

  • Ignore the alarm:

    1. In configuration mode, go to the [edit chassis] hierarchy level.

    2. Ignore the Ethernet link down alarm on the management interface by setting the management-ethernet link-down alarm option to ignore.

See Also

Troubleshooting: Invalid Port Speed Configuration for Junos OS Evolved

Problem

Description

The Invalid Port Speed Configuration alarm is displayed when you run the show system alarms operational mode command.

For example:

Diagnosis

Run the show picd config command from the cli-pfe level to identify invalid port speed configurations. Running the command displays details of port speed/channelization configurations, including which ports are valid and reasons for any invalid PIC configurations.

For example:

Do the results of the show picd config command indicate an invalid port speed configuration?

  • Yes: Continue to resolution.

  • No: Contact Juniper Networks Technical Assistance Center (JTAC) for further assistance.

In the example, the results indicate:

Resolution

To Resolve This Issue

The system alarm was raised for a port speed configuration that was not supported. Configure all ports to a valid port speed to resolve the issue. Port speed is configured at the PIC-level.

Note:

When an invalid configuration is applied on a port, the currently configured speed/channelization on the other ports of the PIC remain in effect until the next reboot of the device or the next picd app restart. After device reboot, or picd restart, all ports of that PIC revert to default speed. The invalid state and the resulting effect of all ports being in default speed remains in effect until the invalid configuration is corrected.

To determine valid port speeds of a logical PIC, run the show chassis pic fpc-slot slot-number pic-slot slot-number command.

The example contains an unsupported port speed/channelization configuration on ports 0/0/12 and 0/0/13. To determine valid port speeds for the example, run show chassis pic fpc-slot 0 pic-slot 0.

The invalid port speed example can be resolved by configuring ports 0/0/12 and 0/0/13 with one of the following valid port speeds:

Troubleshooting: Faulty Ethernet Physical Interface for Junos OS Evolved

You can follow the basic troubleshooting actions as explained in the following topics to troubleshoot an Ethernet physical interface on a device that Junos OS Evolved supports.

Check the Cable Connection

Problem

Description

Packets are not received or transmitted over the Ethernet physical interface.

Diagnosis

  1. Is the correct cable connected to the correct port?

Resolution

Resolve the Cabling Issue

Perform one or more of the following steps to resolve the cabling issue:

  1. Connect the cable properly on the local and remote ends, without any loose connections.

  2. If the existing cable is damaged, replace it with a known good cable.

  3. Connect a single-mode fiber cable to a single-mode interface only and a multimode fiber cable to a multimode interface only. To check fiber optic cable integrity, see Check the Fiber Optic Cable Integrity.

  4. Connect the correct small form-factor pluggable transceiver (SFP) on both sides of the cable.

Check the Fiber Optic Cable Integrity

To check the integrity of the fiber optic cable with an external cable diagnostic testing tool:

Note:

A single-mode fiber cable must be connected to a single-mode interface.

A multi-mode fiber cable must be connected to a multi-mode interface.

  1. Measure the received light level at the receiver (RX) port to see whether the received light level is within the receiver specification of the Ethernet interface.

  2. Measure the transmitted light level at the transmitter (TX) port to see whether the transmitted light level is within the transmitter specification of the Ethernet interface.

Check the Physical Link Status of the Interface

Problem

Description

Unable to transmit or receive packets on the Ethernet interface even though the cable connection is correct.

Solution

To display the physical link status of the interface, run the show interface interface-name media operational mode command. For example, on the et-5/0/1 interface:

Diagnosis

  1. Are there any connectivity problems such as input errors and packet loss even though the Enabled field displays Physical link is Up status and the Active alarms and Active defect field displays None?

  1. Does the Enabled field display Physical link is Down status and the Active alarms and Active defect field display Link?

    • Yes: The interface is either not connected correctly or is not receiving a valid signal. Go to Resolve the Cabling Issue.

    • No: Continue.

Check the Interface Statistics in Detail

Problem

Description

The physical interface is not working even though the Enabled field displays Physical link is Up status and the Active alarms and Active defect field displays None.

Solution

To display the interface statistics in detail, run the show interface interface-name extensive operational command. For example, on the et-5/0/1 interface:

Diagnosis

  1. Does the Policed discards, L2 channel errors, Input DA rejects, or Input SA rejects field display any errors?

Perform the Loopback Diagnostic Test

Problem

Description

The interface cable is connected correctly, and no alarms or errors are associated with the Ethernet physical interface, but the interface is not working.

Solution

To check whether the Ethernet port or PIC is faulty, you must perform the internal loopback test and hardware loopback test.

To perform an internal loopback diagnostic test on an Ethernet interface, for example on et-5/0/1 interface:

  1. In configuration mode, go to the [edit interfaces et-5/0/1] hierarchy level.

  2. Set the ether-options option as loopback, commit the configuration, and quit configuration mode.

  3. In operational mode, execute the show interfaces et-5/0/1 media command.

Note:

Delete the loopback statement after completing your diagnosis.

Execute one of the following steps for a hardware loopback diagnostic test, as needed:

  • For an Ethernet PIC with a fiber optic interface—Physically loop the TX and RX port and check the status of the physical link with the show interfaces interface-name media operational mode command.

  • For an Ethernet PIC with an RJ-45 Ethernet interface—Build a loopback plug by crossing pin 1 (TX +) to pin 3 (RX +) together and pin 2 (TX -) and pin 6 (RX -) together. Then, check the status of the physical link with the show interfaces interface-name media operational mode command.

Diagnosis

  1. Does the Enabled field display Physical link is Up status and the Active alarms and Active defect field display None when you perform the loopback test?

  2. When the Ethernet interface is connected to a remote Ethernet device over multiple patch panels, check to see whether the connection can be looped back at the different patch panels so you can conduct a loopback diagnostic test. Is the loopback diagnostic test successful?

Check for Other Possibilities

Problem

Description

Loopback diagnostic test is successful but unable to transmit and receive packets on the Ethernet interface.

Solution

Use the following commands as needed to troubleshoot an Ethernet interface such as an et-5/0/1 interface:

  • Run the show interfaces interface-name terse operational command to check if the physical interface and logical interfaces are administratively disabled. For example, on an et-5/0/1 interface:

Diagnosis

  1. Does the physical interface and its corresponding logical interfaces display down in the output of the show interfaces interface-name terse operational mode command?

  2. Are the speed, duplex, and auto-negotiation fields in the output of show interfaces interface-name extensive operational mode command set correctly for the interface?

    Note:

    Check if the associated device supports speed and auto-negotiation settings for Flexible PIC Concentrator (FPC).

    • Yes: Check Ethernet Interfaces User Guide for Routing Devices for more troubleshooting tips.

    • No: Contact JTAC for further assistance.

Enable a Physical Interface

To enable a physical interface:

  1. In configuration mode, go to the [edit interfaces] hierarchy level.
  2. Check if the interface is administratively disabled by executing the show command on the interface. For example, on the et-5/0/1 interface:
  3. Enable the interface, and commit.