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New Member

High number of runts, input errors & CRC

When I did a show int gig3/43 on a Catalyst 6513, the output showed a high number of runts, inputs and CRC as shown below. Both the switchport and the PC has been set to 100, Full Duplex.

5 minute output rate 24000 bits/sec, 39 packets/sec

1390359 packets input, 1143788641 bytes, 0 no buffer

Received 18920 broadcasts (17675 multicasts)

163692 runts, 0 giants, 0 throttles

301750 input errors, 138058 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 0 multicast, 0 pause input

0 input packets with dribble condition detected

1975771 packets output, 718733645 bytes, 0 underruns

0 output errors, 0 collisions, 0 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


Re: High number of runts, input errors & CRC


can you clear the counters pertaining to this interface alone and check ?


New Member

Re: High number of runts, input errors & CRC

The combination of these errors may indicate a duplex mismatch (did you get any CDP syslogs?) or a physical problem - cable, nic, or interface. I would say - on the other end of the connection.

Check the cable first, then the interfaces on both sides, just in case, then duplex.

And, do clear counters on the interface as suggested by spremkumar. Your output does not show when they were cleared last time. The errors may well be a result of a past problem.

Hall of Fame Super Silver

Re: High number of runts, input errors & CRC


I know that the original post states that both switch and PC are set to full duplex. But the symptoms that you describe sound a lot like a duplex problem. In particular in my experience large numbers of runts and of CRC errors frequently indicate a full duplex interface that is connected to a half duplex interface. I would suggest that you check the PC carefully and verify what its duplex status is.

When an end station is set for half duplex and begins to transmit a frame it may receive a frame while transmitting. For half duplex station this is an error and it stops transmitting its outgoing frame. If it is less than 64 bytes transmitted it produces a runt. And if it is over 64 bytes transmitted it produces what looks like a normal frame with bad CRC.