Dell PowerConnect 8100 CLI Reference Guide - Page 731

33 Spanning Tree Commands The Multiple Spanning Tree Protocol (MSTP) component complies with IEEE 802.1s by efficiently navigating VLAN traffic over separate interfaces for multiple instances of Spanning Tree. IEEE 802.1D, Spanning Tree and IEEE 802.1w, Rapid Spanning Tree are supported through the IEEE 802.1s implementation. The difference between the RSTP and STP (IEEE 802.1D) is the ability to configure and recognize full-duplex connectivity and ports that are connected to end stations. The difference enables RSTP to rapidly transition to the Forwarding state and to suppress the Topology Change Notification PDUs, where possible. A VLAN ID does not have to be pre-configured before mapping it to an MST instance. Management of MSTP is compliant with the requirements of RFC5060. The following features are supported by Power Connect MSTP: STP Loop Guard - The Loop Guard feature is an enhancement of the Multiple Spanning Tree Protocol. Loop guard protects a network from forwarding loops induced by BPDU packet loss. It can be configured to prevent a blocked port from transitioning to the forwarding state when the port stops receiving BPDUs for some reason (such as a uni-directional link failure). STP BPDU Guard - The STP BPDU guard allows the network administrator to enforce the STP domain borders and keep the active topology consistent and predictable. The switches behind the edge ports that have STP BPDU guard enabled are not able to influence the overall STP topology. At the reception of BPDUs, the BPDU guard operation disables the port that is configured with this option and transitions the port into disable state. This would lead to administrative disable of the port. STP Root Guard - The root guard ensures that the port on which root guard is enabled is the designated port. In a root bridge ports are all designated ports, unless two or more ports of the root bridge are connected together. If the bridge receives superior STP BPDUs on a root guard enabled port, root guard moves this port to a root inconsistent STP state. This root inconsistent state is effectively equal to a listening state. No traffic is forwarded across this Spanning Tree Commands 731