Cable Test

Output from a copper cable test on a Cisco 2960 (old non-X/S/G version) below. For some devices and port types this is service impacting, for others it is not.

In the below output a 100M port shows only 2 of 4 copper pairs as being in use (as that is all that is needed for 100Mbps) and the 1Gbps port shows 4 of 4 pairs as being in use:

LAB-2960#test cable-diagnostics tdr interface Fa0/22
Link state may be affected during TDR test
TDR test started on interface Fa0/22
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

LAB-2960#show cable-diagnostics tdr interface Fa0/22
TDR test last run on: July 30 21:41:31

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Fa0/22    100M  Pair A     8    +/- 15 meters Pair B      Normal
                Pair B     8    +/- 15 meters Pair A      Normal
                Pair C     N/A                Pair D      Not Supported
                Pair D     N/A                Pair C      Not Supported


! Fa0/22 didn't flap but Gi0/4 below did...

LAB-RACK2-2960#test cable-diagnostics tdr interface Gi0/4
TDR test started on interface Gi0/4
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

*Jul 30 21:42:34.915 BST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/4, changed state to down
*Jul 30 21:42:35.931 BST: %LINK-3-UPDOWN: Interface GigabitEthernet0/4, changed state to down
*Jul 30 21:42:42.381 BST: %LINK-3-UPDOWN: Interface GigabitEthernet0/4, changed state to up
*Jul 30 21:42:44.420 BST: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/4, changed state to up


LAB-RACK2-2960#show cable-diagnostics tdr interface Gi0/4
TDR test last run on: July 30 21:42:33

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi0/4     1000M Pair A     0    +/- 10 meters Pair A      Normal
                Pair B     0    +/- 10 meters Pair B      Normal
                Pair C     0    +/- 10 meters Pair C      Normal
                Pair D     0    +/- 10 meters Pair D      Normal

In the following output on a 1Gbps port, 2 pairs show has having a "short" fault, as a result this 1Gbps port has autonegotiated down to 100Mbps:

WS-C2960S-24TS-L#test cable-diagnostics tdr interface Gi1/0/24
TDR test started on interface Gi1/0/24
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

WS-C2960S-24TS-L#show cable-diagnostics tdr interface Gi1/0/24
TDR test last run on: February 15 22:11:10

Interface Speed Local pair Pair length        Remote pair Pair status
--------- ----- ---------- ------------------ ----------- --------------------
Gi1/0/24  100M  Pair A     27   +/- 0  meters Pair B      Normal              
                Pair B     28   +/- 0  meters Pair A      Normal              
                Pair C     28   +/- 1  meters Pair C      Short               
                Pair D     28   +/- 1  meters Pair D      Short  

WS-C2960S-24TS-L#show int gi1/0/24
GigabitEthernet1/0/24 is up, line protocol is up (connected)
  Hardware is Gigabit Ethernet, address is c472.9514.dc18 (bia c472.9514.dc18)
  Description: *** CONNECTION TO 7600 Po1 ***
  MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
     reliability 255/255, txload 73/255, rxload 43/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s, media type is 10/100/1000BaseTX

 

A fibre test can be made using the following command:

test cable-diagnostics prbs start interface Te5/3

show cable-diagnostics prbs interface Te5/3

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