output drops on fastethernet interface

[zong8]

Hi Guys,

I have a fastethernet interface connecting to customer kit and both the connecting interfaces are hard coded to 100/full.

We are seeing output drops in 4 digits in a day on both the interfaces.

The interface is underutilised as its doing close to 15Mbps traffic when it can do 100mbps. Its only 15% utilization so congestion is not an issue in this case.

Could you guys shed some light.

FastEthernet2/32 is up, line protocol is up (connected)
  Hardware is C6k 100Mb 802.3, address is 0007.ecc9.8c0a (bia 0007.ecc9.8c0a)
  Description: xxx
  Internet address is xxx

  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 24/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s
  input flow-control is off, output flow-control is unsupported
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:43, output 00:00:44, output hang never
  Last clearing of "show interface" counters 2d03h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1214
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 41000 bits/sec, 13 packets/sec
  5 minute output rate 9451000 bits/sec, 4230 packets/sec
  L2 Switched: ucast: 34088 pkt, 3109138 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 1452596 pkt, 812879341 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 663675906 pkt, 183244547955 bytes
     1477414 packets input, 840680853 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     663713045 packets output, 195788908561 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

Thanks

Mohammed

[s.marino]

You should check for a hardware failure.  Have you tried other fasethernet ports, cabling and is the result the same?

Sal

[mlund]

Hi Mohammed

There are a very high chance that these output drops are a result of a very short traffic-burst peak. Because the average output rate in this snapshot is over 9M, countered on a 5 minute average.

You can try to lower the average timer to see if the amount of traffic is steady or moving up and down. The lowest timer You can set is 30 seconds.

conf t

int fa2/32

load 30

Also another thing to watch for is if this is a bug/cosmetic error. Sometimes packets count as errors, even if they shouldn't.

I have seen errors that increments exactly one error every minute.

/Mikael

[Ganesh Hariharan]

Hi Guys,
I have a fastethernet interface connecting to customer kit and both the connecting interfaces are hard coded to 100/full.
We are seeing output drops in 4 digits in a day on both the interfaces.
The
interface is underutilised as its doing close to 15Mbps traffic when it
can do 100mbps. Its only 15% utilization so congestion is not an issue
in this case.
Could you guys shed some light.
FastEthernet2/32 is up, line protocol is up (connected)
  Hardware is C6k 100Mb 802.3, address is 0007.ecc9.8c0a (bia 0007.ecc9.8c0a)
  Description: xxx
  Internet address is xxx
  MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, 
     reliability 255/255, txload 24/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 100Mb/s
  input flow-control is off, output flow-control is unsupported 
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:43, output 00:00:44, output hang never
  Last clearing of "show interface" counters 2d03h
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 1214
  Queueing strategy: fifo
  Output queue: 0/40 (size/max)
  5 minute input rate 41000 bits/sec, 13 packets/sec
  5 minute output rate 9451000 bits/sec, 4230 packets/sec
  L2 Switched: ucast: 34088 pkt, 3109138 bytes - mcast: 0 pkt, 0 bytes
  L3 in Switched: ucast: 1452596 pkt, 812879341 bytes - mcast: 0 pkt, 0 bytes mcast
  L3 out Switched: ucast: 663675906 pkt, 183244547955 bytes 
     1477414 packets input, 840680853 bytes, 0 no buffer
     Received 0 broadcasts (0 IP multicast)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 0 multicast, 0 pause input
     0 input packets with dribble condition detected
     663713045 packets output, 195788908561 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
Thanks
Mohammed

Hi Mohammed,

  Following observation can bee taken into account based on the above outputs:-

  The output drop rate 0.00018 %.

Check out the below things to overcome this issue before doing this just Reset the counters using the 'clear counters' command and try the below mentioned steps.

   Minimize periodic broadcast traffic like routing and Service Advertising
   Protocol (SAP) updates (if applicable) by using access lists or by other
   means.

Turn off fast switching for heavily used protocols. For example, turn off
IP fast switching by using the 'no ip route-cache' interface configuration
command.

Hope that helps out your query !!

If helpful do rate the vlauable post.

Regards

Ganesh.H