Understanding Nexus -- Part 15 -- MST

MST is defined in IEEE 802.1s. MST maps multiple VLANs into “instances” that maintain their own STP topology.

• You can have up to 65 MST instances on one device.
• MST is compatible with 802.1d and 802.1w
• You can configure MST to send pre-standard BPDU using the "spanning-tree mst pre-standard" interface command
• The MST configuration for a single region must have the same Name, Revision Number, and VLAN-to-MST Instance Mapping

Enabling MST

switch# config t

switch(config)# spanning-tree mode mst

Entering MST Configuration Mode

switch(config)# spanning-tree mst configuration

switch(config-mst)#

Configuring MST Parameter

switch(config-mst)# name accounting

- Specifies the name for the MST region. The name string has a maximum length of 32 characters and is case sensitive. The default is an empty string

switch(config-mst)# revision 5

- Specifies the revision number for the MST region. The range is from 0 to 65535, and the default value is 0.

switch(config-mst)# instance 1 vlan 10-20

- For instance-id, the range is from 1 to 4094.

Configuring MST Root Bridge

switch# config t

switch(config)# spanning-tree mst 5 root primary

switch(config)# spanning-tree mst 5 root secondary

switch(config)# spanning-tree mst 5 priority 4096