3Com 10014298 manual STP Overview, Configuring STP

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STP OPERATION

	This chapter covers the following topics:
	■	STP Overview
	■	Configuring STP
	■	MSTP Overview
	■	Configuring MSTP
STP Overview	Spanning Tree Protocol (STP) is applied in a loop network to block undesirable
	redundant paths. Using STP avoids the proliferation and infinite cycling of a packet
	in a loop network.
	The fundamental feature of STP is that the switches exchange packets called
	configuration Bridge Protocol Data Units, or BPDU, to decide the topology of the
	network. The configuration BPDU contains the information that ensures that
	switches can compute the spanning tree.
	The configuration BPDU contains the following information:
	■ The root ID consisting of root priority and MAC address
	■ The cost of the shortest path to the root
	■ A designated switch ID consisting of designated switch priority and MAC
		address
	■ A designated port ID consisting of port priority and port number
	■ The age of the configuration BPDU (MessageAge)
	■ The maximum age of the configuration BPDU (MaxAge)
	■ A configuration BPDU interval (HelloTime)
	■ A forward delay of the port (ForwardDelay)
Configuring STP	STP configuration is described in the following sections:
	■ Designating Switches and Ports
	■ Calculating the STP Algorithm

■ Generating the Configuration BPDU

■ Selecting the Optimum Configuration BPDU

■ Designating the Root Port

■ Configuring the BPDU Forwarding Mechanism