C3650-48FQM - cable diagnostic tdr - strange output

[joerg.hohn]

Hi,

we have some C3650-48FQM which shows strange output on "show cable-diagnostics tdr int gi x/y/z"

All connections are 4 wire (2 pair) connections.

switch#sho cable-diagnostics tdr int gi1/0/38

TDR test last run on: August 18 10:39:48



Interface   Speed Local pair Pair length        Remote pair Pair status

---------   ----- ---------- ------------------ ----------- --------------------

Gi1/0/37    auto  Pair A     0    +/- 10 meters N/A         Normal

                  Pair B     0    +/- 10 meters N/A         Normal

                  Pair C     N/A                N/A         Normal

                  Pair D     0    +/- 10 meters N/A         Normal



switch#sho cable-diagnostics tdr int gi1/0/38

TDR test last run on: August 18 10:39:48



Interface   Speed Local pair Pair length        Remote pair Pair status

---------   ----- ---------- ------------------ ----------- --------------------

Gi1/0/38    100M  Pair A     50   +/- 10 meters N/A         Normal

                  Pair B     183  +/- 10 meters N/A         Normal

                  Pair C     4    +/- 5  meters N/A         Open

                  Pair D     4    +/- 5  meters N/A         Open





switch#sho cable-diagnostics tdr int gi1/0/39

TDR test last run on: August 18 10:52:48



Interface   Speed Local pair Pair length        Remote pair Pair status

---------   ----- ---------- ------------------ ----------- --------------------

Gi1/0/39    100M  Pair A     44   +/- 10 meters N/A         Normal

                  Pair B     44   +/- 10 meters N/A         Normal

                  Pair C     7    +/- 10 meters N/A         Normal

                  Pair D     5    +/- 10 meters N/A         Normal

Any suggestions? Is this a bug?

greetings

Jörg

[balaji.bandi]

int gi1/0/38

i would investigate this Physical patches cables, shows more distance ? is this correct ?

Good documentation to understand :

https://community.cisco.com/t5/networking-documents/how-to-use-time-domain-reflectometer-tdr/ta-p/3119327

[Leo Laohoo]

What firmware is the switch running on?

[joerg.hohn]

The switches are running 16.9.4

[Leo Laohoo]

That is one dodgy output.  Personally, I would not trust an output like that. 

What is the uptime of the switch? 

[joerg.hohn]

Hi,

thanks for all your answers and questions.

The switch was booted when checking this but the output was the same strange thing as before the reboot.