no spanning-tree vlan XX ' is automatically inserted into running-conf

[aida.azizi1]

Hello,

we've used Rapid-PVST to prevent L2 loop free in our network infrastructure. the problem is that when the number of vlans exceed 64 then 'no spanning-tree vlan XX ' is automatically inserted into running-config.

It would be nice if I could know the answer of this question, why some switch platform such as 2960x doesn't have any problem with exceeding 64 vlans but other swiches like c2960l or c1000 don't create Spanning-tree instance for inserted vlans.

Another point is that because of having old access switches we are not able to run VTP v3 to configure MST to propagate the MST database instead of Rapid-pvst.

I would like to aks you to guide me how I can find a solution for this issue.

Best regards

[Jon Marshall]

How many STP instances switches support is really a question for Cisco ie. it will probably be down to a hardware limitation on the specific device. 

The obvious question would be whether you need all those vlans on each access switch or whether you could control which vlans are allowed on each switch but assuming you need that many and more then if you can't propagate the MST info you would need to configure each switch manually for it. 

Or upgrade your switches I guess.

Jon

[aida.azizi1]

c2960l and c1000 support only 64 STP instances but c2960x supports more than 64.

via this command:

show spanning-tree summery totals

Name                               Blocking    Listening  Learning Forwarding STP Active
---------------------- -------- --------- -------- ---------- ----------
64 vlans                              0                   0             0              128              128

show vtp status

Feature VLAN:
--------------
VTP Operating Mode : Server
Maximum VLANs supported locally : 256
Number of existing VLANs : 81

the number of existing vlan is 81 but the number of supporting STP instances is 64.

I've already enabled pruning on VTP server in order to eliminate the unused Vlans on the switches automatically.

configuring MST0 is a solution that I've found and works but I'm looking for a optimal solution.

Because of having a lot of access switches in our network it would be difficult to configure the MST with other instances manually.

Although the switch doesn't create the STP instances for inserted vlans there is no L2 loop in the network.

I don't know why.

Regards