During a project where I was onsite I discovered a 20-25 years old network
cabling, called AMPICCS. This cabling system takes one Cat.5 cable,
splits the eight wires into 2x four wires, which serve two ports in a
This type of cabling is limited to 100 MBit / Full duplex and only capable
for 15.4 Watts Power-over-Ethernet. 1 GBit or new wireless access points
which require PoE+ with 30 Watts (like Cisco’s 2800 Series) are not working
with this type of cabling system.
If I encounter a “troublesome” network cabling, I’m always using the following
commands on a Cisco switch for troubleshooting and hunting for Layer one
problems. In my examples shown below, I’m troubleshooting interface Gi1/0/4
on my 3750G Switch:
Show interfaces counters errors
The command show interfaces counters errors outputs the error counters,
where the FCS-Errors are indicating cabling problems. FCS stands for
Field Checksum Sequence.
Show power inline
The command show power inline shows the Power-over-Ethernet usage, which
is useful to check if a device like an IP phone or a wireless access point is
getting the PoE power they need. In this output, it shows my Cisco IP Phone
7975G which consumes 12 Watt.
Test cable-diagnostics tdr interface
The command test cable-diagnostics tdr runs a cable diagnostics test,
with the show cable-diagnostics tdr command the output can be viewed.
The command shows the wire pairs and also the length. This is one of my
Show interfaces transceiver detail
Another one of my favorite commands is show interfaces tranceiver detail,
which provides a lot of information of the SFP or SPF+ modules inserted
into a switch.
Note: Thanks to Heinz Ulm for finding a typo in the commands.