Defining MSTP Properties
The global Multiple Spanning Tree Protocol (MSTP) configures a separate Spanning Tree for each VLAN group and blocks all but one of the possible alternate paths within each Spanning Tree. MSTP allows formation of MST regions that can run multiple MST instances (MSTI). Multiple regions and other STP bridges are interconnected using one single common spanning tree (CST).
MSTP is fully compatible with RSTP bridges, in that an MSTP BPDU can be interpreted by an RSTP bridge as an RSTP BPDU. This not only allows compatibility with RSTP bridges without configuration changes, but also causes any RSTP bridges outside of an MSTP region to see the region as a single RSTP bridge, regardless of the number of MSTP bridges inside the region itself.
For two or more switches to be in the same MST region, they must have the same VLANs to MST instance mapping, the same configuration revision number, and the same region name.
Switches intended to be in the same MST region are never separated by switches from another MST region. If they are separated, the region become two separate regions.
This mapping can be done in the VLAN to MST Instance page.
Configuration on this page applies if the system STP mode is MSTP.
To define MSTP:
- Click Spanning Tree > STP Status and Global Settings. The STP Status and Global Settings page displays. Enable MSTP.
- Click Spanning Tree > MSTP Properties. The MSTP Properties page displays.
- Enter the parameters.
- Region Name--Define an MSTP region name.
- Revision--Define an unsigned 16-bit number that identifies the revision of the current MST configuration. The field range is from 0 to 65535.
- Max Hops--Set the total number of hops that occur in a specific region before the BPDU is discarded. Once the BPDU is discarded, the port information is aged out. The field range is from 1 to 40.
- IST Master--Displays the region’s master.
- Click Apply. The MSTP properties are defined, and the Running Configuration file is updated..