HP ProCurve 5300xl Series Management Manual page 232

Spanning-Tree Operation
802.1s Multiple Spanning Tree Protocol (MSTP)
6-64
Syntax: spanning-tree instance < 1..16 > priority < 0 .. 15 >
This command sets the switch (bridge) priority for the desig­
nated instance. This priority is compared with the priorities
of other switches in the same instance to determine the root
switch for the instance. The lower the priority value, the higher
the priority. (If there is only one switch in the instance, then
that switch is the root switch for the instance.) The root bridge
in a given instance provides the path to connected instances
in other regions that share one or more of the same VLAN(s).
(Traffic in VLANs assigned to a numbered STP instance in a
given region moves to other regions through the root switch
for that instance.)
The priority range for an MSTP switch is 0-61440. However,
this command specifies the instance priority as a multiplier
(0 - 15 ) of 4096. That is, when you specify an instance pri­
ority value of 0 - 15, the actual priority assigned to the switch
for the specified MST instance is:
For example, if you configure "5" as the priority for MST
Instance 1 on a given MSTP switch, then the Switch Priority
setting is 20, 480 for that instance in that switch.
Note: If multiple switches in the same MST instance have the
same priority setting, then the switch with the lowest MAC
address becomes the root switch for that instance.
(instance-priority-value) x 4096