STP instance error

[maxblaze1992]

I am seeing this logs on my switch and its pretty straight forward on what it means 

%SPANTREE_VLAN_SW-2-MAX_INSTANCE: Platform limit of 128 STP instances exceeded. No instance created for VLAN350 (port Gi1/0/10).

Now in our case we are running multi-vendor switch on our infra and i know for a fact that none of them is supporting pvst only rstp my question is should i worry about this error causing routing loops despite the fact that only my root-bridge which happen to be a CISCO-3850 is running rstp-pvst and my other equipment is only running standard rstp?

My theory is it shouldn't cause any issue since vlan350 will only use one single instance on all switches except that cisco ?

Please someone help confirm if i understand correctly.

Thanks,

[Mark Malone]

Hi
My theory is it shouldn't cause any issue since vlan350 will only use one single instance on all switches except that cisco ?

Your correct about the other switches 1 instance for vlan 350 but im thinking the Cisco switch will not even have an STP instance for the vlan 350 which could be an issue, because if using multiple links back to the Cisco switch it may cause a layer 2 loop for that vlan as it doesn't even see recognize it , you may be able to avoid this by setting what specific vlans are allowed on each link with switchport trunk allowed vlan x,x,x. so it doesn't go into a spin , im just thinking here i havent tested this but its just something i thought may cause an issue, all my switches are Cisco and its been a long time since i labbed up stp to test scenarios

[Giuseppe Larosa]

Hello Max,

the real problem is that the Cisco switch will not run any STP instance for the new Vlan 350.

This can lead to problems if Vlan 350 is allowed in multiple redundant links.

You should think of moving to MST in this way you can achieve STP scalability as MST does not run an STP instance for each Vlan but only a few.

MST is compatible with standard RSTP, because MST actually sends out only one BDPU for the instance 0 IST with some additional sections for other MST instances (if any).

This is not something you can ignore, moving to a simple MST configuration is the recommended workaround.

You can configure MST using

spanning-tree mst configuration

name MYCISCO

revision 1

! by default all Vlans are associated to instance 0

! in your case this is enough

! type exit to apply MST config and go back to global configuration

exit

! this command changes the STP mode to MST

spanning-tree mode mst

! to make the Cisco switch the root bridge:

spanning-tree mst 0 priority 0

Hope to help

Giuseppe

Edit:

reviewed MST configuration example to check command syntax.

[maxblaze1992]

what i did is to manually prune the vlan that is not being used on my network on the cisco-SW and spanning-tree instance goes downfrom 128 to double digit.
Since im hesitant to do a major adjustment such as applying MST in my production specially in multi-vendor environment.

anyway thanks for the answer.

[Mark Malone]

MST is an iEEE standard so should work on all your devices unlike PVST but if you have limited the issue hopefully its ok for you