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Troubleshooting Interfaces

 

The below topics discuss the troubleshooting of network interfaces and diagnosing a faulty twisted-pair cable.

Troubleshooting Network Interfaces

Statistics for logical interfaces on Layer 2 interfaces are not accurate

Problem

Description: On QFX5000 switches, statistics for logical interfaces are not supported on Layer 2 interfaces or on any child member interfaces of Layer 2 aggregated Ethernet (AE) interfaces—that is, output for the show interfaces interface-name operational-mode command does not provide accurate I/O information for the logical interfaces.

Solution

If you need to see statistics for those logical interfaces, configure firewall filter rules to collect the information.

The interface on the port in which an SFP or SFP+ transceiver is installed in an SFP or SFP+ module is down

Problem

Description: The switch has an SFP or SFP+ module installed. The interface on the port in which an SFP or SFP+ transceiver is installed is down.

Symptoms: When you check the status with the CLI command show interfaces interface-name , the disabled port is not listed.

Cause

By default, the SFP or SFP+ module operates in the 10-Gigabit Ethernet mode and supports only SFP or SFP+ transceivers. The operating mode for the module is incorrectly set.

Solution

Only SFP or SFP+ transceivers can be installed in SFP or SFP+ modules. You must configure the operating mode of the SFP or SFP+ module to match the type of transceiver you want to use. For SFP+ transceivers, configure 10-Gigabit Ethernet operating mode.

Diagnosing a Faulty Twisted-Pair Cable (CLI Procedure)

Problem

Description: A 10/100/1000BASE-T Ethernet interface has connectivity problems that you suspect might be caused by a faulty cable.

Solution

Use the time domain reflectometry (TDR) test to determine whether a twisted-pair Ethernet cable is faulty.

The TDR test:

  • Detects and reports faults for each twisted pair in an Ethernet cable. Faults detected include open circuits, short circuits, and impedance mismatches.

  • Reports the distance to fault to within 1 meter.

  • Detects and reports pair swaps, pair polarity reversals, and excessive pair skew.

The TDR test is supported on the following switches and interfaces:

  • EX2200, EX2300, EX3200, EX3300, EX3400, EX4200, and EX4300 switches—RJ-45 network interfaces. The TDR test is not supported on management interfaces and SFP interfaces.

  • EX6200 and EX8200 switches—RJ-45 network interfaces on line cards.

Note

We recommend running the TDR test on an interface when there is no traffic on the interface.

To diagnose a cable problem by running the TDR test:

  1. Run the request diagnostics tdr command.
  2. View the results of the TDR test with the show diagnostics tdr command.
  3. Examine the Cable status field for the four MDI pairs to determine if the cable has a fault. In the preceding example, the twisted pair on pins 4 and 5 is broken or cut at approximately one meter from the ge-0/0/10 port connection.
Note

The Test Status field indicates the status of the TDR test, not the cable. The value Passed means the test completed—it does not mean that the cable has no faults.

The following is additional information about the TDR test:

  • The TDR test can take some seconds to complete. If the test is still running when you execute the show diagnostics tdr command, the Test status field displays Started. For example:

  • You can terminate a running TDR test before it completes by using the request diagnostics tdr abort interface interface-name command. The test terminates with no results, and the results from any previous test are cleared.

  • You can display summary information about the last TDR test results for all interfaces on the switch that support the TDR test by not specifying an interface name with the show diagnostics tdr command. For example:

Troubleshooting Uplink Ports on EX2300 Switches

This topic provides troubleshooting information for specific problems related to interfaces on EX2300 switches.

Speeds 10-Mbps and 100-Mbps not supported on uplink ports 4 and 5 on EX2300-48MP switches

Problem

Description: The uplink ports 4 and 5 (see Figure 1) do not support the speeds 10-Mbps and 100-Mbps.

Environment: A transceiver is installed in the uplink port 4 or 5 or both.

Symptoms: When you check the status with the CLI command show interfaces ge or with the J-Web user interface, the port is not listed.

Cause

EX2300-48MP switches do not support 10-Mbps and 100-Mbps speeds on uplink ports 4 and 5. This is an ASIC limitation.

Solution

Use the other ports if you need 10-Mbps and 100-Mbps speeds.