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request diagnostics tdr



Start a time domain reflectometry (TDR) diagnostic test on the specified interface. This test characterizes and locates faults on twisted-pair Ethernet cables. For example, it can detect a broken twisted pair and provide the approximate distance to the break. It can also detect polarity swaps, pair swaps, and excessive skew.

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

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

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


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

You view the results of the TDR test with the show diagnostics tdr command.



Stop the TDR test currently in progress on the specified interface. No results are reported, and previous results, if any, are cleared.


The name of the interface.


Start a TDR test on the specified interface.

Required Privilege Level


Output Fields

Table 1 lists the output fields for the request diagnostics tdr command. Output fields are listed in the approximate order in which they appear.

Table 1: request diagnostics tdr Output Fields

Field Name

Field Description

Test Status

Information about the status of the TDR test request:

  • Admin Down interface-name—The interface is administratively down. The TDR test cannot run on interfaces that are administratively down.

  • Interface interface-name not found—The interface does not exist.

  • Test successfully executed interface-name—The test has successfully started on the interface. You can view the test results with the show diagnostics tdr command.

  • VCT not supported on interface-name—The TDR test is not supported on the interface.

Sample Output

request diagnostics tdr start interface ge-0/0/19

Release Information

Command introduced in Junos OS Release 9.0.