Interpreting Output from a Cisco Interface

Parameter	Description
runts	A frame that is smaller than the medium’s minimum frame size (e.g. 64 Bytes on an Ethernet network) and has a bad CRC
giants	A frame that is larger than the medium’s maximum frame size (e.g. 1518 Bytes on a non-jumbo frame Ethernet network) and has a bad CRC
input errors	Sum of an interface’s errors, including: runts, giants, no buffer, CRC, frame, overrun and ignore errors.
output errors	The total number of errors that prevented a packet from being transmitted.
collisions	The number of times a collision occurred (common on shared Ethernet networks running in half-duplex mode).
late collisions	The number of times a collision “late” in the transmission. (NOTE: “Late” means a time greater than the medium’s slot time, which is twice the time required for a bit to transmit the maximum distance of a medium (e.g. Later than 51.2 microseconds for 10 Mbps Ethernet, 5.12 microseconds for 100 Mbps Ethernet, and 4.096 microseconds for 1 Gbps Ethernet)).
CRC	The number of times the cyclical redundancy check (CRC) value calculated for a frame upon transmission is different than the CRC value calculated for a frame when it is received.

Example Interface with Errors

#show interfaces GigabitEthernet3/41

GigabitEthernet3/41 is up, line protocol is up (connected)
  Hardware is C6k 1000Mb 802.3, address is 0013.5f61.8c00 (bia 0013.5f61.8c00)
  Description: Example Interface
  Internet address is xxx.xxx.xxx.xxx/xx
  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, 
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Half-duplex, 10Mb/s, media type is 10/100/1000BaseT
  input flow-control is off, output flow-control is off
  Clock mode is auto
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:50, output 03:03:27, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
  L2 Switched: ucast: 11348897 pkt, 726329408 bytes - mcast: 75 pkt, 18192 bytes
  L3 in Switched: ucast: 93140312 pkt, 7082202293 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 77380906 pkt, 4867676639 bytes mcast: 0 pkt, 0 bytes
     106408519 packets input, 8419210713 bytes, 0 no buffer
     Received 1890273 broadcasts (0 IP multicasts)
     29027 runts, 0 giants, 0 throttles 
     29027 input errors, 29027 CRC, 1 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     77388865 packets output, 5108257688 bytes, 0 underruns
     0 output errors, 18494 collisions, 3 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier, 0 PAUSE output
     0 output buffer failures, 0 output buffers swapped out