[c-nsp] quick spanning tree question

[Cord MacLeod]

On Mar 29, 2010, at 9:06 PM, Octavio Alvarez wrote:

> On Fri, 26 Mar 2010 23:47:47 -0700, Cord MacLeod <cordmacleod at gmail.com> wrote:
> 
>> 3 days ago traffic started showing up on the trunk port connecting my top of rack switches.  Each of these switches has it's own better trunk path to the root bridge.  I can't see why any traffic at all would traverse these links unless the other trunk on g0/45 was down, which it isn't.  Also, spanning tree doesn't claim any topology changes.
> 
> There's very little information. I could even think your traffic is
> real and STP doesn't have anything to do with it.

Sorry for the late reply.  Here is some more information.  First, the traffic is over 50mbit, I don't think it's STP.  Second:

switch3#show spanning-tree interface g0/46

Vlan             Role Sts Cost      Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
VLAN0001         Desg FWD 4         128.46   P2p 
VLAN0100         Desg FWD 4         128.46   P2p 
VLAN0101         Desg FWD 4         128.46   P2p 
VLAN0102         Altn BLK 4         128.46   P2p 
VLAN0120         Desg FWD 4         128.46   P2p 
VLAN0200         Desg FWD 4         128.46   P2p 
VLAN0231         Desg FWD 4         128.46   P2p 
VLAN0250         Desg FWD 4         128.46   P2p 
VLAN0321         Desg FWD 4         128.46   P2p 
VLAN0450         Desg FWD 4         128.46   P2p 
VLAN0777         Desg FWD 4         128.46   P2p 
VLAN0888         Desg FWD 4         128.46   P2p 

switch3#sh spanning-tree root             

                                        Root    Hello Max Fwd
Vlan                   Root ID          Cost    Time  Age Dly  Root Port
---------------- -------------------- --------- ----- --- ---  ------------
VLAN0001         24577 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0100         24676 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0101         24677 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0102         20582 0018.181b.d700         7    2   20  15  Gi0/45          
VLAN0120         24696 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0200         24776 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0231         24807 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0250         24826 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0321         24897 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0450         25026 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0777         25353 0017.e0d7.e180         4    2   20  15  Gi0/45          
VLAN0888         25464 0017.e0d7.e180         4    2   20  15  Gi0/45          

switch3#show spanning-tree summary 
Switch is in pvst mode
Root bridge for: none
Extended system ID           is enabled
Portfast Default             is disabled
PortFast BPDU Guard Default  is disabled
Portfast BPDU Filter Default is disabled
Loopguard Default            is disabled
EtherChannel misconfig guard is enabled
UplinkFast                   is disabled
BackboneFast                 is disabled
Configured Pathcost method used is short

Name                   Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0001                     0         0        0          2          2
VLAN0100                     0         0        0          9          9
VLAN0101                     0         0        0          2          2
VLAN0102                     1         0        0          1          2
VLAN0120                     0         0        0         19         19
VLAN0200                     0         0        0         16         16
VLAN0231                     0         0        0          2          2
VLAN0250                     0         0        0          2          2
VLAN0321                     0         0        0          5          5
VLAN0450                     0         0        0          2          2
VLAN0777                     0         0        0          2          2
VLAN0888                     0         0        0          2          2
---------------------- -------- --------- -------- ---------- ----------
12 vlans                     1         0        0         64         65

switch3#show int g0/46        
GigabitEthernet0/46 is up, line protocol is up (connected)
...
  MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, 
     reliability 255/255, txload 5/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive not set
  Full-duplex, 1000Mb/s, link type is auto, media type is 10/100/1000BaseTX
  input flow-control is off, output flow-control is unsupported 
  ARP type: ARPA, ARP Timeout 04:00:00
  Last input 00:00:00, output 00:00:00, 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 59995000 bits/sec, 3555 packets/sec
     1446844033 packets input, 479111376008 bytes, 0 no buffer
     Received 35695615 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 watchdog, 35604297 multicast, 0 pause input
     0 input packets with dribble condition detected
     10988444843 packets output, 4655746445035 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


Does this give enough information?  From my understanding of spanning tree, g0/46 should not be used for any traffic.  g0/45 is the root port for all vlans.