Output packets dropped

Unanswered Question
Sep 11th, 2007

Can you explain why I'm receiving excessive output drops on the following interface and what can be done to resolve it.

gh5-c4506-2#sh int port-channel 16

Port-channel16 is up, line protocol is up (connected)

Hardware is EtherChannel, address is 000f.2386.e328 (bia 000f.2386.e328)

Description: .... Etherchannel for unix server rack

MTU 1500 bytes, BW 4000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 1000Mb/s, media type is N/A

input flow-control is off, output flow-control is unsupported

Members in this channel: Gi5/41 Gi5/42 Gi5/43 Gi5/44

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

Last input 5d15h, output never, output hang never

Last clearing of "show interface" counters never

Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops: 97166753

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 4341000 bits/sec, 540 packets/sec

5 minute output rate 1287000 bits/sec, 417 packets/sec

246065750 packets input, 348619887609 bytes, 0 no buffer

Received 116910 broadcasts (98024 multicast)

0 runts, 0 giants, 0 throttles

527460 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 input packets with dribble condition detected

718036014 packets output, 889508674274 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

gh5-c4506-2#

I have this problem too.
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amritpatek Mon, 09/17/2007 - 06:28

You may get output drops because of bursty traffic. In such a case you can increase the size of the output queue and also monitor the CPU and memory usage. If the issue is not with bursty traffic check for the speed and duplex settings of the link. If speed and duplex settings are fine I would suggest that you try and implement some etherchannel load balancing over this link to help compensate for the traffic that is filling up your output queue buffer on these ports. I would also suggest that you try implementing flow control to see if this helps to alleviate the issue.

mell0ns23 Mon, 09/17/2007 - 07:31

Thanks for the feedback Amritpatek. I'll take your suggestions into consideration.

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