[c-nsp] Strange switchport traffic problem

[Tassos Chatzithomaoglou]

You could put a sniffer and check the kind of packets.
Probably some broadcasts/unknown unicasts are sent over there.

Try removing all vlans from the trunk and check if the packets decrease.

--
Tassos

Eric Van Tol wrote on 17/6/2008 3:17 μμ:
> Hi all,
> I am encountering a strange problem that I don't think I've ever seen before.  I've got an ME3400-12CS switch with an 'up/up' interface that is showing no traffic on the input/output rate counters, but the 'packets output' and 'bytes output' counters are incrementing.  Also, my NMS is showing about 4-5Mb/s output on this port.  Here's the port config and 'show int' output - timestamp shows timespan and rate of increase:
> 
> interface GigabitEthernet0/2
>  switchport trunk allowed vlan 50,51
>  switchport mode trunk
>  load-interval 30
> end
> 
> switch1#clear count gi0/2
> Clear "show interface" counters on this interface [confirm]
> switch1#sh int gi0/2
> Load for five secs: 7%/0%; one minute: 6%; five minutes: 6%
> Time source is NTP, 08:08:07.812 EDT Tue Jun 17 2008
> 
> GigabitEthernet0/2 is up, line protocol is up (connected)
>   Hardware is Gigabit Ethernet, address is 001e.f6d2.d902 (bia 001e.f6d2.d902)
>   MTU 9000 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 1/255, rxload 0/255
>   Encapsulation ARPA, loopback not set
>   Keepalive set (10 sec)
>   Full-duplex, 1000Mb/s, 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 never, output 00:00:01, output hang never
>   Last clearing of "show interface" counters 00:00:03
>   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 0 bits/sec, 0 packets/sec
>   30 second output rate 0 bits/sec, 0 packets/sec
>      4 packets input, 280 bytes, 0 no buffer
>      Received 0 broadcasts (4 multicasts)
>      0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 watchdog, 4 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      2188 packets output, 1583091 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
> switch1#sh int gi0/2
> Load for five secs: 8%/0%; one minute: 6%; five minutes: 6%
> Time source is NTP, 08:08:11.880 EDT Tue Jun 17 2008
> 
> GigabitEthernet0/2 is up, line protocol is up (connected)
>   Hardware is Gigabit Ethernet, address is 001e.f6d2.d902 (bia 001e.f6d2.d902)
>   MTU 9000 bytes, BW 1000000 Kbit, DLY 10 usec,
>      reliability 255/255, txload 1/255, rxload 0/255
>   Encapsulation ARPA, loopback not set
>   Keepalive set (10 sec)
>   Full-duplex, 1000Mb/s, 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 never, output 00:00:05, output hang never
>   Last clearing of "show interface" counters 00:00:07
>   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 0 bits/sec, 0 packets/sec
>   30 second output rate 0 bits/sec, 0 packets/sec
>      9 packets input, 890 bytes, 0 no buffer
>      Received 0 broadcasts (9 multicasts)
>      0 runts, 0 giants, 0 throttles
>      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
>      0 watchdog, 9 multicast, 0 pause input
>      0 input packets with dribble condition detected
>      4529 packets output, 2910397 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
> 
> Any ideas on what this might be?  I have another port on the same switch, configured pretty much the exact same way and I'm not seeing this weirdness.
> 
> -evt
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