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New Member

Input errors

I have a 2811 with the latest IOS on it and my interface FA0/0 is constantly counting up input errors.

I have changed the cable set the speed and duplex and tried auto for both sides. There are no errors on the switch, but I changed the port on the switch just for fun. :)

Here is my show interface fa0/0

Router#sh inter fa0/0

FastEthernet0/0 is up, line protocol is up

Hardware is MV96340 Ethernet, address is 0014.f201.5be0 (bia 0014.f201.5be0)

Description: $ETH-LAN$Router interface

Internet address is

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 22/255, rxload 6/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, 100BaseTX/FX

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters 00:26:07

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 2364000 bits/sec, 1828 packets/sec

5 minute output rate 8649000 bits/sec, 1552 packets/sec

2949726 packets input, 543040449 bytes

Received 14995 broadcasts, 0 runts, 0 giants, 0 throttles

3559 input errors, 0 CRC, 0 frame, 0 overrun, 3559 ignored

0 watchdog

0 input packets with dribble condition detected

2491240 packets output, 1725241583 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 output buffer failures, 0 output buffers swapped out

Any idea what this could be or should I even worry about it?


Re: Input errors


Input errors are related to no buffer, runt, giant, CRC, frame, overrun, ignored, and abort.

Other input-related errors can also increment the count, so this sum might not balance with the other counts.

No buffer errors occur when a packet is discarded because there was no buffer space. Broadcast storms on Ethernet networks are often responsible for no buffer events. Compare with ignored.

Runts are packets that are discarded because they are smaller than the medium's minimum packet size. Any Ethernet packet that is less than 64 bytes is considered a runt.

Giants are packets that are discarded because they are larger than the medium's maximum packet size. Any Ethernet packet that is more than 1,518 bytes is considered a giant.

CRC = cyclic redundancy check. A CRC error occurs when the CRC generated by the originating station or far-end device does not match the checksum calculated from the data received. On a LAN, this usually indicates noise or transmission problems on the LAN interface or the LAN bus. A high number of CRCs is usually the result of collisions or a station transmitting bad data.

Framing errors occur when packets are received with a CRC error and a noninteger number of octets. On a LAN, this is usually the result of collisions or a malfunctioning Ethernet device.

Overruns represent the number of times that the receiver hardware is unable to hand received data to a hardware buffer because the input rate exceeds the receiver's ability to handle the data.

Ignored packets are those that are discarded because the interface hardware does not have enough internal buffers. Broadcast storms and bursts of noise can result in an increased number of ignored packets. Compare with no buffer.


New Member

Re: Input errors

Ok, so what does this tell me? I have read all that on as well but where should I go next?

I also have my show buffers with failures on the small but not on the big buffers, so that is being taken care of.



Re: Input errors


You can use the show buffers input-interface [interface type] [interface number] header command to find out the types of that packets fill up the input queue.




Cisco Employee

Re: Input errors

You use that command ONLY when the traffic is being proces-switched. That wont help you with ignored packets. Ignored means we are over subscribing the interface. This over subscription is of the hardware buffers, not software. The command you gave is for software buffers.

To fix this issue you need to lower the amount of traffic on the link, possibly using MQC with a shaper down stream or lowering the amount of traffic or just by replacing with a faster interface that can handle the load. Its also important to note that these can also be produced by IOS defects from time to time. Are you seeing any performance issues?

New Member

Re: Input errors

They do occationally have issues with voice breaking up, which passes through this link.


Re: Input errors

Hi Dave

In that case (also pointed out by Anthnoy) you need to have MQC with LLQ configured for Voice traffic so that your voice really doesn't have any hit during congestion.

Having said that you can configure CBWFQ for other traffic patterns so that the minimum guarantee can be assured for other applications too..