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Unexpected BPDU Packet from an empty switch

lebanonit
Level 1
Level 1

I have a 3750 Stack on my network with several VLANs.  One of these VLANs is 100.

I configured a switch that is also using vlan 100 on every port.  I plug a cable from a port on my stack to the newly configured switch with nothing else plugged into that new switch and I get Unexpected BPDU packet on the stack and the port is shut down. 

 

FastEthernet1/0/2 is down, line protocol is down (err-disabled)
  Hardware is Fast Ethernet, address is 0013.7f0c.1c04 (bia 0013.7f0c.1c04)
  Description: None
  MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Auto-duplex, Auto-speed, 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 00:00:15, output never, output hang never
  Last clearing of "show interface" counters never
  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 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     9 packets input, 1507 bytes, 0 no buffer
     Received 6 broadcasts (6 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 6 multicast, 0 pause input
     0 input packets with dribble condition detected
     37 packets output, 4730 bytes, 0 underruns
     0 output errors, 0 collisions, 6 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

 

On the New Switch it says

 

FastEthernet0/1 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0011.5c00.3101 (bia 0011.5c00.3101)
  MTU 1522 bytes, BW 100000 Kbit, DLY 100 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Auto-duplex, Auto-speed, 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 00:04:28, output 00:04:27, output hang never
  Last clearing of "show interface" counters never
  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 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     22 packets input, 2492 bytes, 0 no buffer
     Received 22 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 8 multicast, 0 pause input
     0 input packets with dribble condition detected
     6 packets output, 1004 bytes, 0 underruns
     0 output errors, 0 collisions, 1 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

 

Nothing else is plugged into that switch I just connected.  Any idea why I am getting this?

7 Replies 7

Richard Burts
Hall of Fame
Hall of Fame

It sounds like the new switch sent a spanning tree BPDU on its port, which would be expected behavior if it is configured as a normal access port. It sounds like the 3750 did not expect to receive a BPDU. Can you post config of the 3750 (at least the config of the interface and of show run | inc span).

 

HTH

 

Rick

HTH

Rick

interface FastEthernet1/0/2
 description 100
 switchport access vlan 100
 switchport mode access
 spanning-tree portfast

 

Is this what you are looking for?

That is the configuration of the interface and it looks quite normal. Could you also post the output of these commands

show run | inc span

show spanning-tree

 

I am wondering if something like BPDUGUARD is enabled.

 

HTH

 

Rick

HTH

Rick

Here is the output with the commands specified:

 

show run | inc span
spanning-tree mode mst
spanning-tree portfast bpduguard default
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id
spanning-tree backbonefast
spanning-tree mst configuration
spanning-tree mst 1 priority 24576
no spanning-tree vlan 34,100
 spanning-tree portfast
 spanning-tree portfast
 spanning-tree portfast
 spanning-tree portfast
 spanning-tree portfast
 spanning-tree portfast
 spanning-tree portfast
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spanning-tree portfast

 

show spanning-tree

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    0
             Address     2880.2346.9460
             Cost        220000
             Port        135 (GigabitEthernet3/1/3)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32768  (priority 32768 sys-id-ext 0)
             Address     001e.13a1.ee80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi2/0/1             Desg FWD 20000     128.55   P2p Edge
Fa2/0/2             Desg FWD 200000    128.58   P2p Edge
Fa2/0/4             Desg FWD 200000    128.60   P2p Edge
Fa2/0/7             Desg FWD 200000    128.63   P2p Edge
Fa2/0/8             Desg FWD 200000    128.64   P2p Edge
Fa2/0/10            Desg FWD 200000    128.66   P2p Edge
Fa2/0/11            Desg FWD 200000    128.67   P2p Edge
Fa2/0/12            Desg FWD 200000    128.68   P2p Edge
Fa2/0/13            Desg FWD 200000    128.69   P2p Edge
Fa2/0/18            Desg FWD 200000    128.74   P2p Edge
Fa2/0/20            Desg FWD 200000    128.76   P2p Edge
Fa2/0/22            Desg FWD 200000    128.78   P2p Edge
Fa2/0/25            Desg FWD 200000    128.83   P2p Edge
Fa2/0/27            Desg FWD 200000    128.85   P2p Edge
Fa2/0/30            Desg FWD 200000    128.88   P2p Edge
Fa2/0/31            Desg FWD 200000    128.89   P2p Edge
Fa2/0/35            Desg FWD 200000    128.93   P2p Edge
Fa2/0/36            Desg FWD 200000    128.94   P2p Edge
Fa2/0/38            Desg FWD 200000    128.96   P2p Edge
Fa2/0/40            Desg FWD 200000    128.98   P2p Edge
Fa2/0/41            Desg FWD 200000    128.99   P2p Edge
Fa2/0/42            Desg FWD 200000    128.100  P2p Edge
Gi1/0/1             Desg FWD 20000     128.1    P2p Edge
Fa1/0/2             Desg FWD 200000    128.4    P2p Bound(STP)
Fa1/0/8             Desg FWD 200000    128.10   P2p Edge
Fa1/0/9             Desg FWD 200000    128.11   P2p Edge
Fa1/0/11            Desg FWD 200000    128.13   P2p Edge
Fa1/0/12            Desg FWD 200000    128.14   P2p Edge
Fa1/0/13            Desg FWD 200000    128.15   P2p Edge
Fa1/0/16            Desg FWD 200000    128.18   P2p Edge
Fa1/0/18            Desg FWD 200000    128.20   P2p Edge
Fa1/0/19            Desg FWD 200000    128.21   P2p Edge
Fa1/0/20            Desg FWD 200000    128.22   P2p Edge
Gi1/0/3             Desg FWD 20000     128.27   P2p Edge
Gi1/0/4             Desg FWD 20000     128.28   P2p Edge
Fa1/0/26            Desg FWD 200000    128.30   P2p Edge
Fa1/0/27            Desg FWD 200000    128.31   P2p Edge
Fa1/0/31            Desg FWD 200000    128.35   P2p Edge
Fa1/0/38            Desg FWD 200000    128.42   P2p Edge
Fa1/0/39            Desg FWD 200000    128.43   P2p Edge
Fa1/0/42            Desg FWD 200000    128.46   P2p Edge
Fa1/0/43            Desg FWD 200000    128.47   P2p Edge
Fa1/0/46            Desg FWD 200000    128.50   P2p Edge
Gi3/0/1             Desg FWD 20000     128.109  P2p
Gi3/0/2             Desg FWD 20000     128.110  P2p Edge
Gi3/0/5             Desg FWD 20000     128.113  P2p Edge
Gi3/0/6             Desg FWD 200000    128.114  P2p Edge
Gi3/0/7             Desg FWD 20000     128.115  P2p Edge
Gi3/0/8             Desg FWD 200000    128.116  P2p Edge
Gi3/0/9             Desg FWD 20000     128.117  P2p Edge
Gi3/0/11            Desg FWD 20000     128.119  P2p Edge
Gi3/0/12            Desg FWD 20000     128.120  P2p Edge
Gi3/0/13            Desg FWD 20000     128.121  P2p Edge
Gi3/0/14            Desg FWD 20000     128.122  P2p Edge
Gi3/0/15            Desg FWD 20000     128.123  P2p Edge
Gi3/0/16            Desg FWD 20000     128.124  P2p Edge
Gi3/0/17            Desg FWD 20000     128.125  P2p
Gi3/0/18            Desg FWD 20000     128.126  P2p
Gi3/0/19            Desg FWD 20000     128.127  P2p Edge
Gi3/0/20            Desg FWD 200000    128.128  P2p Edge
Gi3/0/21            Desg FWD 20000     128.129  P2p
Gi3/0/22            Desg FWD 20000     128.130  P2p
Gi3/0/23            Desg FWD 20000     128.131  P2p
Gi3/0/24            Desg FWD 20000     128.132  P2p
Gi3/1/1             Desg FWD 20000     128.133  P2p
Gi3/1/3             Root FWD 20000     128.135  P2p
Gi3/1/4             Desg FWD 20000     128.136  P2p

 

MST1
  Spanning tree enabled protocol mstp
  Root ID    Priority    24577
             Address     001e.13a1.ee80
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    24577  (priority 24576 sys-id-ext 1)
             Address     001e.13a1.ee80
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi2/0/1             Desg FWD 20000     128.55   P2p Edge
Fa2/0/2             Desg FWD 200000    128.58   P2p Edge
Fa2/0/4             Desg FWD 200000    128.60   P2p Edge
Fa2/0/7             Desg FWD 200000    128.63   P2p Edge
Fa2/0/8             Desg FWD 200000    128.64   P2p Edge
Fa2/0/10            Desg FWD 200000    128.66   P2p Edge
Fa2/0/11            Desg FWD 200000    128.67   P2p Edge
Fa2/0/12            Desg FWD 200000    128.68   P2p Edge
Fa2/0/13            Desg FWD 200000    128.69   P2p Edge
Fa2/0/18            Desg FWD 200000    128.74   P2p Edge
Fa2/0/20            Desg FWD 200000    128.76   P2p Edge
Fa2/0/22            Desg FWD 200000    128.78   P2p Edge
Fa2/0/25            Desg FWD 200000    128.83   P2p Edge
Fa2/0/27            Desg FWD 200000    128.85   P2p Edge
Fa2/0/30            Desg FWD 200000    128.88   P2p Edge
Fa2/0/31            Desg FWD 200000    128.89   P2p Edge
Fa2/0/35            Desg FWD 200000    128.93   P2p Edge
Fa2/0/36            Desg FWD 200000    128.94   P2p Edge
Fa2/0/38            Desg FWD 200000    128.96   P2p Edge
Fa2/0/40            Desg FWD 200000    128.98   P2p Edge
Fa2/0/41            Desg FWD 200000    128.99   P2p Edge
Fa2/0/42            Desg FWD 200000    128.100  P2p Edge
Gi1/0/1             Desg FWD 20000     128.1    P2p Edge
Fa1/0/2             Desg FWD 200000    128.4    P2p Bound(STP)
Fa1/0/8             Desg FWD 200000    128.10   P2p Edge
Fa1/0/9             Desg FWD 200000    128.11   P2p Edge
Fa1/0/11            Desg FWD 200000    128.13   P2p Edge
Fa1/0/12            Desg FWD 200000    128.14   P2p Edge
Fa1/0/13            Desg FWD 200000    128.15   P2p Edge
Fa1/0/16            Desg FWD 200000    128.18   P2p Edge
Fa1/0/18            Desg FWD 200000    128.20   P2p Edge
Fa1/0/19            Desg FWD 200000    128.21   P2p Edge
Fa1/0/20            Desg FWD 200000    128.22   P2p Edge
Gi1/0/3             Desg FWD 20000     128.27   P2p Edge
Gi1/0/4             Desg FWD 20000     128.28   P2p Edge
Fa1/0/26            Desg FWD 200000    128.30   P2p Edge
Fa1/0/27            Desg FWD 200000    128.31   P2p Edge
Fa1/0/31            Desg FWD 200000    128.35   P2p Edge
Fa1/0/38            Desg FWD 200000    128.42   P2p Edge
Fa1/0/39            Desg FWD 200000    128.43   P2p Edge
Fa1/0/42            Desg FWD 200000    128.46   P2p Edge
Fa1/0/43            Desg FWD 200000    128.47   P2p Edge
Fa1/0/46            Desg FWD 200000    128.50   P2p Edge
Gi3/0/1             Desg FWD 20000     128.109  P2p
Gi3/0/2             Desg FWD 20000     128.110  P2p Edge
Gi3/0/5             Desg FWD 20000     128.113  P2p Edge
Gi3/0/6             Desg FWD 200000    128.114  P2p Edge
Gi3/0/7             Desg FWD 20000     128.115  P2p Edge
Gi3/0/8             Desg FWD 200000    128.116  P2p Edge
Gi3/0/9             Desg FWD 20000     128.117  P2p Edge
Gi3/0/11            Desg FWD 20000     128.119  P2p Edge
Gi3/0/12            Desg FWD 20000     128.120  P2p Edge
Gi3/0/13            Desg FWD 20000     128.121  P2p Edge
Gi3/0/14            Desg FWD 20000     128.122  P2p Edge
Gi3/0/15            Desg FWD 20000     128.123  P2p Edge
Gi3/0/16            Desg FWD 20000     128.124  P2p Edge
Gi3/0/17            Desg FWD 20000     128.125  P2p
Gi3/0/18            Desg FWD 20000     128.126  P2p
Gi3/0/19            Desg FWD 20000     128.127  P2p Edge
Gi3/0/20            Desg FWD 200000    128.128  P2p Edge
Gi3/0/21            Desg FWD 20000     128.129  P2p
Gi3/0/22            Desg FWD 20000     128.130  P2p
Gi3/0/23            Desg FWD 20000     128.131  P2p
Gi3/0/24            Desg FWD 20000     128.132  P2p
Gi3/1/1             Desg FWD 20000     128.133  P2p
Gi3/1/3             Desg FWD 20000     128.135  P2p
Gi3/1/4             Desg FWD 20000     128.136  P2p

I typed in

no spanning-tree portfast

that made the problem go away.  I am not sure that is the best solution though.

 

If you typed that in on just the port connecting to the switch stack then that is the correct thing to do. 

 

You should not have portfast enabled on any ports that interconnect switches. 

 

Jon

Thanks for the outputs. They do confirm that I was on the right track and that bpduguard is enabled.

spanning-tree portfast bpduguard default

 

I agree with Jon that disabling it on that particular interface is the correct solution.

 

HTH

 

Rick

HTH

Rick
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