2960 switch Total Output Drops?

razorbakill · ‎07-05-2011

I have a 48 port 2960 switch with 2 10/100 ports ( fa0/46-47) setup in an etherchannel with a 2950 48 port switch. I am getting total output drops on port fa0/47.

Below is some show commands, anyone have any idea's why this would be?

FastEthernet0/47 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0026.ca81.c02f (bia 0026.ca81.c02f)

Description: trunk Etherchannel link to fa0/47 switch in server

oom

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

reliability 255/255, txload 2/255, rxload 51/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100BaseTX

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

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

Last input 00:00:03, output 00:00:05, output hang never

Last clearing of "show interface" counters 4d23h

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 19175

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 20011000 bits/sec, 1904 packets/sec

5 minute output rate 877000 bits/sec, 1395 packets/sec

1427492496 packets input, 1872808936374 bytes, 0 no buffer

Received 2762778 broadcasts (2074949 multicasts)

0 runts, 0 giants, 0 throttles

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

0 watchdog, 2074949 multicast, 0 pause input

0 input packets with dribble condition detected

772408291 packets output, 340903564586 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

FastEthernet0/46 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 0026.ca81.c02e (bia 0026.ca81.c02e)

Description: trunk Etherchannel link to fa0/46 switch in server r

oom.

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

reliability 255/255, txload 1/255, rxload 9/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100BaseTX

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

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

Last input 00:00:20, output 00:00:00, output hang never

Last clearing of "show interface" counters 5d00h

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 3600000 bits/sec, 380 packets/sec

5 minute output rate 141000 bits/sec, 76 packets/sec

193394062 packets input, 239902766720 bytes, 0 no buffer

Received 37177 broadcasts (37175 multicasts)

0 runts, 0 giants, 0 throttles

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

0 watchdog, 37175 multicast, 0 pause input

0 input packets with dribble condition detected

302728942 packets output, 28654958491 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

Switch#show platform port-asic stats drop fa0/47

Interface Fa0/47 TxQueue Drop Statistics

Queue 0

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Queue 1

Weight 0 Frames 25903

Weight 1 Frames 6

Weight 2 Frames 0

Queue 2

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Queue 3

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Switch#show platform port-asic stats drop fa0/46

Interface Fa0/46 TxQueue Drop Statistics

Queue 0

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Queue 1

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Queue 2

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 0

Queue 3

Weight 0 Frames 0

Weight 1 Frames 0

Weight 2 Frames 69845

Switch#sh int po1 counters errors

Port Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize OutDiscard

s

Po1 0 0 0 0 0 1919

5

Port Single-Col Multi-Col Late-Col Excess-Col Carri-Sen Runts

Giants

Po1 0 0 0 0 0 0

paolo bevilacqua · ‎07-06-2011

Below is some show commands, anyone have any idea's why this would be?

That there is more traffic than 100 Mbs, consequently packets are dropped.

If you don't want drops, use gigabit.

Joseph W. Doherty · ‎07-06-2011

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Posting

Oversubscription of any port's bandwidth will eventually result in drops.

In your posted example, I notice there appears to be a (temporary?) load imbalance between the two ports. Changing the Etherchannel hash algorithm, if possible, might better distribute the load across both links and perhaps reduce the occurrence of oversubscription.

If your oversubscription is transient, adjusting buffer resource allocations might also reduce the occurrence of drops. This might especially pertain to your traffic as your hardware queue drop stats only show drops on two queues for one weight.