[c-nsp] Large amounts of undersize packets

[Mattias Eliasson]

Hello

I have a SFP LX/LH interface in a 3560G that has no errors in "sh int" 
but massive undersize packets (500-4000/s) in "show interface counters 
error.

The interface is switching about 70/40Mbit of data and never more then 
200Mbit.

The other device is a GSR (partner) where they see giants on there port.

There is no problem with the traffic flow, no packetloss etc etc.


Output

interface GigabitEthernet0/26
  switchport trunk encapsulation dot1q
  switchport trunk allowed vlan 15
  switchport mode trunk
end

GigabitEthernet0/26 is up, line protocol is up (connected)
   Hardware is Gigabit Ethernet, address is 0016.c785.cb1a (bia 
0016.c785.cb1a)
   MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
      reliability 255/255, txload 14/255, rxload 10/255
   Encapsulation ARPA, loopback not set
   Keepalive not set
   Full-duplex, 1000Mb/s, link type is auto, media type is 1000BaseLX SFP
   input flow-control is off, output flow-control is unsupported
   ARP type: ARPA, ARP Timeout 04:00:00
   Last input 26w6d, output 00:00:00, output hang never
   Last clearing of "show interface" counters 00:21:32
   Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
   Queueing strategy: fifo
   Output queue: 0/40 (size/max)
   30 second input rate 41777000 bits/sec, 5190 packets/sec
   30 second output rate 58074000 bits/sec, 11185 packets/sec
      6719065 packets input, 2436706204 bytes, 0 no buffer
      Received 0 broadcasts (0 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
      15710756 packets output, 1518701210 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



Port        Align-Err    FCS-Err   Xmit-Err    Rcv-Err UnderSize
*snip*
Gi0/26              0          0          0          0   3997338
*snip*

What would cause this behaviour?

Mattias Eliasson

Teknikmejeriet AB
ISP
Sweden