SMC Networks SMC8624/48T manual 208

SPANNING TREE COMMANDS

Command Usage

• Spanning Tree Protocol

Uses RSTP for the internal state machine, but sends only 802.1D BPDUs. This creates one spanning tree instance for the entire network. If multiple VLANs are implemented on a network, the path between specific VLAN members may be inadvertently disabled to prevent network loops, thus isolating group members. When operating multiple VLANs, we recommend selecting the MSTP option.

• Rapid Spanning Tree Protocol

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 after a port’s migration delay timer expires, the switch assumes that 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.

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