Spanning Tree instance maximum

[clifford.gormley]

Hello

I read that there is a limit of 128 spanning-tree instances per switch if using PVST, and that any instances greater than 128 do not us spanning-tree.

Does the switch indicate that the 128-instance limit has been reached?  Or do you just need to determine this by using SHOW SPANNING-TREE XXXX commands?
Thanks           

[Reza Sharifi · Accepted solution]

Hi,

Not sure exactly what the error message would be if you try to configure more then 128 instances, but if you are planning to have 129 instances, you would need to delete one of the existing instance before you can add the 129th instance.

sh span-tree will show you one vlan per instance, but the numbers don't necessary corelate  For example: if you have 2 instances in your switch, the vlans for these instance can be 250 and 270.

HTH

[InayathUlla Sharieff]

HI,

In PVST+ or rapid-PVST+ mode, the switch or switch stack supports up to 128 spanning-tree instances.

In MSTP mode, the switch or switch stack supports up to 65 MST instances. The number of VLANs that can be mapped to a particular MST instance is unlimited

cmd:

sh spanning-tree summary totals

Below you can see the instance active for vlans.

also you get the following error message if 128 instances are over:

***** Platform limit of 128 STP instances exceeded. No instance created for VLAN190

Ref:

http://ieoc.com/forums/p/5975/20666.aspx

HTH

Regards

Inayath

*Plz rate all usefull posts.

[Sandeep Sharma]

Hi Reza

Yes you will see the platform limit error message when you cross your STP instance.

######Platform limit of 128 STP instances exceeded

Thanks & Regards

Sandeep

[clifford.gormley]

Thank you all!

I selected the first response, even though you all gave great info.

Not sure how to 'share' the correct answer.

Cliff

[InayathUlla Sharieff]

Hi Clifford,

Its already marked answered.

Regards

Inayath