Underruns and output buffer failures

[mikaly001]

Hi

I have two Catalyst 3550 connecting two datacenter and I'm receiving errors on connecting switchports. Errors are output buffer failures and underruns. Is it just that switches are running out of resources or what? We are using servers in the datacenters with nfs and I'v heard that this could cause these errors. I'd really appreciate a opinion from a network professional.

Here are port statistics. Both switchports are identical.

FastEthernet0/3 is up, line protocol is up

Hardware is Fast Ethernet, address is 000c.301f.c503 (bia 000c.301f.c503)

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

reliability 255/255, txload 3/255, rxload 6/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s

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

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 21:54:22

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue :0/40 (size/max)

1 minute input rate 2676000 bits/sec, 531 packets/sec

1 minute output rate 1432000 bits/sec, 528 packets/sec

123525330 packets input, 166317380 bytes, 0 no buffer

Received 887720 broadcasts, 0 runts, 0 giants, 0 throttles

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

0 watchdog, 671127 multicast, 0 pause input

0 input packets with dribble condition detected

108650060 packets output, 322356071 bytes, 11269 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

11269 output buffer failures, 0 output buffers swapped out

Thanks

[Georg Pauwen]

Hello,

most likely, the erros are caused by your link being saturated.

I found a previous post which explains the error as following:

'The frames are being switched in hardware, since there are no output queue drops. But the hardware is attempting to put frames on the wire when it's pretty close to being saturated. Although your 1 minute average is only around 1,5 mbit, it only takes a couple millisecond long burst to fill up the hardware interface buffers and cause this error. It's probably time to add another link (forming an etherchannel) or jump to a gig interface. I don't think you can tune these hardware buffers at all to buy any additional time.'

Conclusion: your link is getting overloaded...

Regards,

GP

[arun.kumar3]

There are underruns reportd in the output. This is because the Far-end transmitter faster than the near-end receiver.

Recommendation - consider buffer or Q tuning. I problem persists upgrade the hardware.