Use the cable-diagnostic feature to test cables in the event where there might be a bad copper cable.
NOTE: This feature is only available on non-SFP copper ports.
Enter diagnostics
to open up the diagnostics menu:
switch# diagnostics
Once done, the diagnostics command set is now available for use, and the cable-diagnostics command can be executed:
switch# diag cable-diagnostic <IFACE>
6300# diagnostics <CR>
6300# diag ?
asic ASIC diagnostics
audit-failure-notification Configure audit failure notification
bgp IP information
cable-diagnostic Cable diagnostic test
...snip for brevity
6300# diag cable-diagnostic ?
IFNAME