Spanning-Tree Operation 
802.1s Multiple Spanning Tree Protocol (MSTP) 
priority < 0..15 > 
MSTP uses this parameter to determine the port(s) to use 
for forwarding. The port with the lowest priority number 
has the highest priority. The range is 0 to 240, and is 
configured by specifying a multiplier in the range of 0 -
15. For example, to enter a priority of 64 you would 
configure Priority with a multiplier of  4; that is, (4 x 16 
= 64). Thus, the displayed default setting of 128 is derived 
from the default multiplier of 8. When you use the show 
spanning-tree command options, the Priority appears as 
the result of the multiplier x 16, and not the multiplier 
itself. (Default: 128; configured multiplier = 8). 
Configuring MST Instance Parameters 
Command  Page 
spanning-tree instance < 1..16 > vlan < vid> [ vid..vid ]  6-61 
no spanning-tree instance < 1..16 > 
spanning-tree instance < 1..16 > priority < 0..15 >  6-63 
spanning-tree priority < 0..15 >  6-64 
Syntax:  spanning-tree instance < 1..16 > vlan < vid [ vid..vid ] > 
no spanning-tree instance < 1..16 > 
Configuring MSTP on the switch automatically configures the 
IST instance and places all statically configured VLANs on the 
switch into the IST instance. This command creates a new 
MST instance (MSTI) and moves the VLANs you specify from 
the IST to the MSTI.  At least one VLAN must be mapped to a 
MSTI when you create it. (A VLAN cannot be mapped to more 
than one instance at a time.) You can create up to 16 MSTIs 
in a region. Use the no form of the command to remove a VLAN 
from an MSTI. (Removing a VLAN from an MSTI returns the 
VLAN to the IST instance, where it can either remain or be re-
assigned to another MSTI configured in the region.) 
The no form of the command deletes the specified MSTI and 
returns all VLAN assignments to the region’s IST instance. 
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