Common Cisco switch port errors

From my experience the most network problems are on Layer 1 (Physical layer aka "The cable"). Cisco switches provide a lot of information of the switch interfaces and typically I check:


swt-3750g#show interfaces counters errors
swt-3750g#show interfaces status
swt-3750g#show interfaces GigabitEthernet x/x/x
Cisco IOS show interface commands

Align-Err
Malformed frames, bad hardware, duplex mismatch, half duplex collisions
FCS-Err
Bad frame checksum, duplex mismatch, bad hardware
Xmit-Err
Speed settings mismatch
Rcv-Err
Duplex mismatch, backplane congestion
UnderSize
Received frames which are less than 64 bytes
OutDiscards
Occur when transmit buffer is full and packets are dropped
Single-Col
Half duplex, duplex mismatch, high utilization of port
Multi-Col
Half duplex, duplex mismatch, high utilization of port
Late-Col
Cable length, duplex mismatch
Excess-Col
Switch rehad 16 collisions in row, high utilization of port
Carri-Sen
Duplex settings
Runts
Frame is smaller than 64 bytes and has bad CRC, duplex settings, physical port
Giants
Frame is larger than 1518 bytes and has bad FCS, device source
Common Cisco switch port errors

For me, the quick info above is okay before I look into the details and start troubleshooting. Cisco has a good document on their website at Troubleshooting Switch Port and Interface Problems which covers every aspect.

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