3Com 3C17300A Implementation Guide - Page 40

40 CHAPTER 4: USING RESILIENCE FEATURES The protocol is a part of the IEEE 802.1D bridge specification. To explain STP more effectively, your Switch will be referred to as a bridge. Rapid Spanning Tree Protocol (RSTP) The Rapid Spanning Tree (RSTP) is an enhanced Spanning Tree feature. RSTP implements the Spanning Tree Algorithm and Protocol, as defined in the IEEE 802.1w standard. RSTP is enabled by default. 3Com recommends that you use the Rapid Spanning Tree Protocol feature (enabled by default) to provide optimum performance for your network and ease of use. Some of the benefits of RSTP are: ■ Faster determination of the Active Spanning Tree topology throughout a bridged network. ■ Support for bridges with more than 256 ports. ■ Support for Fast-Forwarding configuration of edge ports provided by the 'Fast Start' feature. Fast Start allows a port that is connected to an endstation to begin forwarding traffic after only four seconds; this "Auto" setting is default for front panel ports. During these four seconds RSTP (or STP) will detect any misconfiguration that may cause a temporary loop and react accordingly. If you have Fast Start disabled on a port, the Switch will wait for 30 seconds before RSTP (or STP) lets the port forward traffic. If you set Fast Start to "Enable" mode, ports enter the forwarding mode immediately after becoming active. This mode should be used for ports connected to edge devices in an AppleTalk network. ■ Easy deployment throughout a legacy network, through backward compatibility: ■ it will default to sending 802.1D style BPDU's on a port if it receives packets of this format. ■ it is possible for some ports on a Switch to operate in RSTP (802.1w) mode, and other ports, for example those connected to a legacy Switch, to operate in STP (802.1D) mode. ■ you have an option to force your Switch to use the legacy 802.1D version of Spanning Tree, if required.