SMC Networks SMC6824M manual 161, Basic Configuration of Global Settings

SPANNING TREE ALGORITHM CONFIGURATION

•Rapid Spanning Tree Protocol8

RSTP supports connections to either STP or RSTP nodes by monitoring the incoming protocol messages and dynamically adjusting the type of protocol messages the RSTP node transmits, as described below:

-STP Mode – If the switch receives an 802.1D BPDU (i.e., STP BPDU) after a port’s migration delay timer expires, the switch assumes it is connected to an 802.1D bridge and starts using only 802.1D BPDUs.

-RSTP Mode – If RSTP is using 802.1D BPDUs on a port and receives an RSTP BPDU after the migration delay expires, RSTP restarts the migration delay timer and begins using RSTP BPDUs on that port.

•Multiple Spanning Tree Protocol

-To allow multiple spanning trees to operate over the network, you must configure a related set of bridges with the same MSTP configuration, allowing them to participate in a specific set of spanning tree instances.

-A spanning tree instance can exist only on bridges that have compatible VLAN instance assignments.

-Be careful when switching between spanning tree modes. Changing modes stops all spanning-tree instances for the previous mode and restarts the system in the new mode, temporarily disrupting user traffic.

Command Attributes

Basic Configuration of Global Settings

•Spanning Tree State – Enables/disables STA on this switch. (Default: Enabled)

•Spanning Tree Backup Root – Automatically lowers the switch’s bridge priority by 4096 if it loses contact with the current root device. To succeed, the switch must have a direct connection to current root bridge, and its adjusted bridge priority must be higher (i.e., a numerically lower value) than all the other bridges in the spanning tree. (Default: Disabled)

•Spanning Tree Type – Specifies the type of spanning tree used on this switch:

-STP: Spanning Tree Protocol (IEEE 802.1D; i.e., when this option is selected, the switch will use RSTP set to STP forced compatibility mode)

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