STP problem in vlans

[rezamira]

hi guys

i have a strange problem

i have two cisco 3850 stack switches and add all vlans on it

when i use "show spanning-tree summary" command, just 128 vlan shown

and when i use "sho run | s vlan" displays:

no spanning-tree vlan 1138-1243,1245-1467,1470-1533,1555-1563,1565-1576,1580
no spanning-tree vlan 1581-1582,1585,1589-1590,1592,1630-1635,1800,1900,2001
no spanning-tree vlan 2003,2010,2100,2228,2504,2526,2550,2610,2624,2650-2653
no spanning-tree vlan 2660,2700-2709,2720-2724,2726-2727,2790,2800-2802,2804
no spanning-tree vlan 2820-2825,4000,4092

BTW, this vlans doesnt work correctly and i cannot correct them

is there anybody can help me?
regards

Reza

[Reza Sharifi]

Hi Reza,

Can you post the output of "sh run" and "sh vlan" from the switch stack?

Reza

[rezamira]

its another thing i see

i deleted all vlan

and define again, after adding more and more, "no spanning-tree vlan ...." appear in show run

i told this maybe help

regards

Reza

[mlund]

Hi

128 is the limitation of spanning-tree instances, see this link

https://www.cisco.com/en/US/docs/switches/lan/catalyst3850/software/release/3se/consolidated_guide/b_consolidated_3850_3se_cg_chapter_01001001.html#ID352

/Mikael

[rezamira]

Dear Mikael
thanks for your reply
if maximum stp support number is 128, so what will be happen in networks has more than 128 vlans and cannot use MST, im sure there is a way for this

regards
Reza

[mlund · Accepted solution]

Hi

Those times I run into this issue I used the "switchport trunk allowed vlan <>" on the core switch to remove unnecessary vlans. Also I used vtp transparent on the edge switches so they will not learn of vlans not needed, and then only activate the vlans that are needed. That way I only had to use those vlans that actually are needed on the edge switches. Be aware of the limitation that is different on different hardware.

If you miss this there is a risk for loops in the network if spanning-tree is not running for a vlan.

/Mikael