Specifications

Switching create mstp msti 8-91
Software Release 2.7.3
C613-03098-00 REV A
create mstp msti
Syntax CREate MSTp MSTI=instance [PRIOrity=0..65535]
where instance is the instance number assigned to the new MSTI. It has the
range 1-4094.
Description This command creates a new multiple spanning tree instance (MSTI) on the
switch. The multiple spanning tree algorithm enables a collection of VLANs to
be associated with a particular spanning tree instance. Within this instance,
frames belonging to this VLAN group are forwarded over the active topology
established by that particular instance's spanning tree. Frames for VLAN
groups belonging to other instances each have their own active topologies.
Once an MSTI has been successfully created, VLANs can be added to it by
using the command add mstp msti vlan.
Within each MST region, the MSTP maintains multiple spanning tree instances
(MSTIs). A unique instance number identifies each single MSTI.
The MSTI parameter specifies the instance number of the multiple spanning
tree instance (MSTI) being created. Although numbers can be assigned within
the range 1 to 4094, the maximum number of MSTIs within each region, or
switch, is 64. Instance number 0 is reserved for the common internal spanning
tree (CIST) instance.
The MSTI number is very useful because it identifies a particular instance
within an MST region.
The priority parameter sets the value of the priority field contained in the
bridge identifier. The bridge identifier comprises two parts: a bridge priority
part (more significant), and a bridge address part (less significant). The
multiple spanning tree algorithm uses the bridge identifier when determining
the role of a switch within each spanning tree. The switch with a lower priority
is considered to have better bridge identifier, and is therefore more likely to be
chosen as the root bridge. The CIST and each MSTI have their own individual
priority parameter, so the roles of the same switch could be different in the
CIST and each MSTI by tuning the bridge priority. The priority value operates
in multiples of 4096. If you specify a value that is not a multiple of 4096, this
will be rounded down to the nearest multiple of 4096, see Table 8-19 on
page 8-92.The default switch priority is 32768.