16 IntroductionSpanning Tree Protocol FeaturesSpanning Tree Protocol (STP)802.1d Spanning tree is a standard Layer 2 switch requirement that allows bridges to automatically preventand resolve L2 forwarding loops. Switches exchange configuration messages using specifically formattedframes and selectively enable and disable forwarding on ports.For more information, see "Configuring the Spanning Tree Protocol" on page 275.Fast LinkSTP can take up to 30-60 seconds to converge. During this time, STP detects possible loops, allowing timefor status changes to propagate and for relevant devices to respond. 30-60 seconds is considered too long ofa response time for many applications. The Fast Link option bypasses this delay, and can be used in networktopologies where forwarding loops do not occur.For more information enabling Fast Link for ports and LAGs, see "Defining STP Port Settings" on page 280or "Defining STP LAG Settings" on page 285.IEEE 802.1w Rapid Spanning TreeSpanning Tree can take 30-60 seconds for each host to decide whether its ports are actively forwardingtraffic. Rapid Spanning Tree (RSTP) detects uses of network topologies to enable faster convergence,without creating forwarding loops.For more information, see "Configuring Rapid Spanning Tree" on page 287.STP Root GuardRoot guard restricts the interface from functioning as the root port for the switchMultiple Spanning Tree (MSTP)MTSP operation maps VLAN into STP instances. Multiple spanning tree provides differing load balancingscenario. Packet assigned to various VLANs are transmitted along different paths within Multiple SpanningTree Regions(MST Regions). Regions are one or more Multiple Spanning Tree Bridges by which frames canbe transmitted.Link AggregationFor more information, see "Aggregating Ports" on page 324.Link AggregationUp to eight Aggregated Links may be defined, each with up to eight member ports, to form a single LinkAggregated Group (LAG). This enables:• Fault tolerance protection from physical link disruption• Higher bandwidth connections
