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STP Instances

Hi Guys,

 

I am little confused about the stp instance calculation.

 

Can you pls conform the number instances from the below outputs and how we are calculating it ?

 

UPE_CS01_LKO#show spanning-tree sum
UPE_CS01_LKO#show spanning-tree summary
Switch is in pvst mode
Root bridge for: VLAN0001, VLAN0011-VLAN0021, VLAN0025, VLAN0031-VLAN0033
  VLAN0051-VLAN0052, VLAN0055, VLAN0061-VLAN0064, VLAN0066, VLAN0071
  VLAN0101-VLAN0102, VLAN0275, VLAN0279, VLAN0286, VLAN0300-VLAN0301, VLAN031
  VLAN0320-VLAN0321, VLAN0327, VLAN0358, VLAN0383
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          9          9
VLAN0011                     0         0        0         16         16
VLAN0012                     0         0        0          3          3
VLAN0013                     0         0        0          2          2
VLAN0014                     0         0        0          6          6
VLAN0015                     0         0        0          8          8
 --More--         
Name                   Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0016                     0         0        0          2          2
VLAN0017                     0         0        0         14         14
VLAN0018                     0         0        0          3          3
VLAN0019                     0         0        0          3          3
VLAN0020                     0         0        0          2          2
VLAN0021                     0         0        0          2          2
VLAN0025                     0         0        0          4          4
VLAN0031                     0         0        0          6          6
VLAN0030                     0         0        0          4          4
VLAN0033                     0         0        0          4          4
VLAN0051                     0         0        0          4          4
VLAN0052                     0         0        0          4          4
VLAN0055                     0         0        0          8          8
VLAN0061                     0         0        0          3          3
VLAN0062                     0         0        0          3          3
VLAN0063                     1         0        0          2          3
VLAN0064                     0         0        0          3          3
VLAN0066                     0         0        0          4          4
VLAN0071                     0         0        0          2          2
VLAN0101                     0         0        0          2          2
VLAN0102                     0         0        0          2          2
VLAN0275                     0         0        0          4          4
VLAN0279                     0         0        0          2          2
 --More--         
Name                   Blocking Listening Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
VLAN0286                     0         0        0          2          2
VLAN0300                     0         0        0          4          4
VLAN0302                     0         0        0          4          4
VLAN0315                     0         0        0          5          5
VLAN0320                     0         0        0          5          5
VLAN0321                     0         0        0          4          4
VLAN0335                     0         0        0          4          4
VLAN0427                     0         0        0          4          4
VLAN0458                     0         0        0          4          4
VLAN0483                     0         0        0          2          2
---------------------- -------- --------- -------- ---------- ----------
39 vlans                     1         0        0        169        170

 

It is calculated by the vlan number's or active STP ??

1 REPLY 1
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Rising star

Hi

For evry vlan you add, cisco will by default, start an stp instance. You can disable stp per vlan. If you haven't done that, you have 39 stp instances.

There are often limits on how many stp instances a switch can handle. So if you enabla more vlan than the switch can handle stp for, there will be vlan that doesn' run stp. Different switch models can have different limits.

/Mikael

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