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Table Of Contents
Command Mode CONFIGURATION
Usage Information RSTP determines the root bridge but you can assign one bridge a lower priority to increase the probability of it
being the root bridge. A lower priority value increases the probability of the bridge becoming a root bridge.
Example
OS10(config)# spanning-tree rstp priority 5002
Supported Releases 10.2.0E or later
Multiple Spanning-Tree
MSTP is one of the variations of the rapid spanning-tree protocol that mitigates some of the challenges of RPVST+. RPVST+ allows a
spanning-tree instance for each VLAN. This 1:1 approach is not suitable if you have multiple VLANs — each spanning-tree instance costs
bandwidth and processing resources. You can congure Multiple Spanning-Tree Instances (MSTIs) and map multiple VLANs to one
spanning-tree instance to reduce the total number of instances. For more information on RPVST+, see RPVST+.
When you enable MST, all ports in Layer 2 (L2) mode participate in MST. OS10 only supports one MST region.
You can achieve load balancing using the MST protocol (MSTP). For example, as shown in the following gure, when you map three VLANs
to two multiple spanning-tree instances (MSTIs), VLAN 100 trac takes a dierent path than VLAN 200 and 300 trac.
Conguring MST is a four-step process:
1 Enable MST, if the current running spanning-tree protocol (STP) version is not MST.
2 (Optional) Map the VLAN to dierent instances in such a way that the trac is load balanced well and the link utilization is ecient.
3 Ensure the same region name is congured in all the bridges running MST.
4 (Optional) Congure the revision number. The revision number is the same on all the bridges.
Congure MSTP
When you enable MST globally, all switch ports, port-channels, and VLAN interfaces get automatically assigned to MSTI zero (0). In a
MSTI, only one path is enabled for forwarding.
• Enable MST in CONFIGURATION mode.
spanning-tree mode mst
Congure and verify MSTP
OS10(config)# spanning-tree mode mst
OS10(config)# do show spanning-tree
show spanning-tree mst configuration
Layer 2
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