[c-nsp] 4506 - disconnected ports generating traffic?

[Higham, Josh]

I have a very strange bug and am not getting much from my ticket with
Cisco.  I have a switch that has physically disconnected interfaces that
show as up, are generating traffic (input, plus output drops), and logs
show MAC addresses flapping between these interfaces.  Plugging a cable
in (whether or not there is a device at the other end), in some cases
stopped this from happening.

 

Has anyone run across this or similar behavior?

 

1     6  Sup II+10GE 10GE (X2), 1000BaseX (SFP) WS-X4013+10GE      

 2    48  10/100/1000BaseT (RJ45)V, Cisco/IEEE   WS-X4548-GB-RJ45V  

 3    48  10/100/1000BaseT (RJ45)V, Cisco/IEEE   WS-X4548-GB-RJ45V  

 4    48  10/100/1000BaseT (RJ45)V, Cisco/IEEE   WS-X4548-GB-RJ45V  

 5    48  10/100/1000BaseT (RJ45)V, Cisco/IEEE   WS-X4548-GB-RJ45V  

 6    48  10/100/1000BaseT (RJ45)V, Cisco/IEEE   WS-X4548-GB-RJ45V  

 

This interface has nothing connected to it, but not the output drops and
input traffic

 

CLT-ACCESS-B2F1-1#sho int g5/27

GigabitEthernet5/27 is up, line protocol is up (connected)

  Hardware is Gigabit Ethernet Port, address is 0023.5e78.744a (bia
0023.5e78.744a)

  MTU 1500 bytes, BW 100000 Kbit, DLY 10 usec, 

     reliability 255/255, txload 229/255, rxload 229/255

  Encapsulation ARPA, loopback not set

  Keepalive set (10 sec)

  Full-duplex, 100Mb/s, link type is auto, media type is 10/100/1000-TX

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

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

  Last input 05:03:57, output never, output hang never

  Last clearing of "show interface" counters 00:02:41

  Input queue: 0/2000/0/0 (size/max/drops/flushes); Total output drops:
59099365

  Queueing strategy: fifo

  Output queue: 0/40 (size/max)

  30 second input rate 89862000 bits/sec, 45921 packets/sec

  30 second output rate 89862000 bits/sec, 45921 packets/sec

     6696953 packets input, 1638126423 bytes, 0 no buffer

     Received 6696922 broadcasts (88192 multicasts)

     0 runts, 0 giants, 0 throttles

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

     0 input packets with dribble condition detected

     6696953 packets output, 1638126423 bytes, 0 underruns

 

These two interfaces have nothing connected:

 

.Jun 14 00:11:35.578 UTC: %C4K_EBM-4-HOSTFLAPPING: Host CI:SC:OX:XX:XX
in vlan 4 is flapping between port Gi5/28 and port Gi5/25

 

(the MAC address that is flapping is from the core switch that this
access switch is linked to)

 

Here is the interface configuration:

 

interface GigabitEthernet5/27

 power inline auto max 7900

 switchport access vlan 4

 switchport trunk encapsulation dot1q

 switchport trunk native vlan 4

 switchport trunk allowed vlan 4,25

 switchport mode access

 load-interval 30

 qos trust dscp

 tx-queue 1

   bandwidth percent 25

 tx-queue 2

   bandwidth percent 25

 tx-queue 3

   bandwidth percent 30

   priority high

   shape percent 30

 tx-queue 4

   bandwidth percent 20

 no cdp enable

 

Thanks for any help or thoughts about what to look at or check.

 

Josh Higham