Configuring Ethernet Ports Using TDR Cable Diagnostics
OmniSwitch AOS Release 8 Network Configuration Guide December 2017 page 1-13
Using TDR Cable Diagnostics
Time Domain Reflectometry (TDR) is a feature that is used to detect cable faults. This feature is best
deployed in networks where service providers and system administrators want to quickly diagnose the
state of a cable during outages, before proceeding with further diagnosis.
When a TDR test is initiated, a signal is sent down a cable to determine the distance to a break or other
discontinuity in the cable path. The length of time it takes for the signal to reach the break and return is
used to estimate the distance to the discontinuity.
Initiating a TDR Cable Diagnostics Test
Consider the following guidelines before initiating a TDR test:
• Only one test can run at any given time, and there is no way to stop a test once it has started.
• The TDR test runs an “out-of-service” test; other data and protocol traffic on the port is interrupted
when the test is active.
• TDR is supported only on copper ports.
• TDR is not supported on Link aggregate ports.
• Each time a TDR test is run, statistics from a test previously run on the same port are cleared.
A TDR test is initiated using the interfaces tdr CLI command. For example, the following command
starts the test on port 2/1:
-> interfaces 1/1/1 tdr enable
Displaying TDR Test Results
The show interfaces tdr-statisticscommand is used to display TDR test statistics. For example:
-> show interfaces 1/1/1 tdr-statistics
Legend:
Pair 1 - Orange and White
Pair 2 - Green and White
Pair 3 - Blue and White
Pair 4 - Brown and White
Ch/Slot/ No of Cable Fuzzy Pair1 Pair1 Pair2 Pair2 Pair3 Pair3 Pair4 Pair4 Test
port pairs State Length State Length State Length State Length State Length Result
-----+-----+------+-----+-----+-----+------+------+-----+------+-----+------+------
1/1/1 4 ok 0 ok 3 ok 3 ok 3 ok 3 success
The following cable states are indicated in the show interfaces tdr-statistics command output:
• OK—Wire is working properly
• Open:—Wire is broken
• Short—Pairs of wire are in contact with each other
• Crosstalk—Signal transmitted on one pair of wire creates an undesired effect in another wire.
• Unknown:—Cable diagnostic test unable to find the state of a cable.
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