Dell PowerConnect 55xx Systems User Guide 23FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Maintenance Projects\DellContax\sources\CxUGFeatures.fmD E L L C O N F I D E N T I A L – P R E L I M I N A R Y 1 0 / 3 0 / 1 3 - F O R P R O O F O N LYFast LinkSTP can take 30–60 seconds to converge. During this time, STP detectspossible loops, enabling time for status changes to propagate and for relevantdevices to respond. This period of 30-60 seconds is considered too long aresponse time for many applications. The Fast Link option bypasses thisdelay, and can be used in network topologies, where forwarding loops do notoccur.For more information on enabling Fast Link for ports and LAGs, see "STPPort Settings" on page 443 or "Static Addresses" on page 425.IEEE 802.1w Rapid Spanning TreeSpanning Tree takes 30–60 seconds for each host to decide whether its portsare actively forwarding traffic. Rapid Spanning Tree (RSTP) detects uses ofnetwork topologies to enable faster convergence, without creating forwardingloops.For more information, see "Spanning Tree" on page 435.IEEE 802.1s Multiple Spanning TreeMultiple Spanning Tree (MSTP) operation maps VLANs into STP instances.MSTP provides a different load balancing scenario. Packets assigned to variousVLANs are transmitted along different paths within MSTP Regions (MSTRegions). Regions are one or more MSTP bridges by which frames can betransmitted. The standard lets administrators assign VLAN traffic tounique paths.For more information, see "Spanning Tree" on page 435.STP BPDU GuardBPDU Guard is used as a security mechanism, to protect the network frominvalid configurations.BPDU Guard is usually used either when fast link ports (ports connected toclients) are enabled or when the STP feature is disabled. When it is enabledon a port, the port is shut down if a BPDU message is received and anappropriate SNMP trap is generated.For more information, see "Spanning Tree" on page 435.
