MST Configuration

[RS19]

I have Cisco 2960 switch & I am going to use MST for spanning tree

Below is the configuration

spanning-tree mst configuration
 name TEST-MST
 revision 1
 instance 1 vlan 101
 instance 1 vlan 102

I have 2 VLANS & I want to add both the VLANs into instance 1. 

There will be only 1 instance.

Would like to know, technically if this is possible.

[Marvel]

Hi RS19,

Technically, 2 VLANs can be configured on Instance 1 and they can be verified as well. 

[RS19]

Thanks.

But I will not be configuring or using any VLANs in Instance 2.

Only VLANs in instance 1. No instance 2 will be used.

My understanding it should be fine.

[Marvelleous]

Yes, indeed.

[Marvelleous]

--

[Marvel]

Hi @RS19,

You can do configuration like this: 

SW>enable
SW#configure terminal
SW(config)#spanning-tree mode mst
SW(config)#spanning-tree mst configuration
SW(config-mst)#revision 1
SW(config-mst)#name TEST-MST
SW(config-mst)#instance 1 vlan 101, 102
SW(config-mst)#exit
SW(config)#spanning-tree mst 1 priority 16384
SW(config)#end

SW#show spanning-tree mst 1

##### MST1    vlans mapped:   101,102
Bridge        address 0014.a964.2e00  priority      32769 (32768 sysid 1)
Root          address 0014.f2d2.4180  priority      16384  (8192 sysid 1)
              port    Fa0/10          cost          200000    rem hops 19

 Regards

[Deepak Kumar]

Hi,

Yes, it is possible and this is the default behavior of the MST (run Single instant of STP for multiple VLANs). If this switch is in the production then my recommendation for migration step by step as like:

1. Configure MST configuration on all switches.

spanning-tree mst configuration
  revision 1
  name TEST-MST
   instance 1 vlan 101, 102

2. Decide a Root bridge as per your network topology, hardware resources, etc. (take care of PVST simulation)

 spanning-tree mst 1 priority 4096/0 <Priority as per your network configuration>

3. now migrate from PVTS to MST

spanning-tree mode mst