D-Link DES-3326S manual Bridge Protocol Data Units

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

chance of a given port being elected as the root port

Port Cost	A value	used	by STP	to	19 – 100Mbps
	evaluate	paths	–	STP	Fast Ethernet
	calculates	path	costs	and	ports
	selects the path with the
	minimum cost as the active				10	–
	path.				1000Mbps
					Gigabit
					Ethernet
					ports

Table 5-5. STP Parameters – Port Group Level

Bridge Protocol Data Units

For STP to arrive at a stable network topology, the following information is used:

•The unique switch identifier

•The path cost to the root associated with each switch port

•The port identifier

STP communicates between switches on the network using Bridge Protocol Data Units (BPDUs). Each BPDU contains the following information:

•The unique identifier of the switch that the transmitting switch currently believes is the root switch

•The path cost to the root from the transmitting port

•The port identifier of the transmitting port

The switch sends BPDUs to communicate and construct the spanning-tree topology. All switches connected to the LAN on

Switch Management and Operating Concepts 61