Intel 470 manual Spanning Tree Protocol

C H A P T E R 2 Intel® NetStructure™ 470T and 470F Switches User Guide

The switch checks the amount of broadcast traffic on each port every 20 seconds. If the port detects that the amount of broadcast traffic exceeds the upper threshold on two subsequent checks, the port drops all broadcast traffic.

When broadcast traffic is dropped for storm control, the switch continues to check the amount of broadcast traffic on each port. For the port to begin accepting broadcast traffic again, the amount of broadcast traffic must fall below the lower threshold percentage. The lower threshold percentage, 1%, is a factory default. If broadcast traffic falls below the lower threshold percentage when the port is checked, the switch automatically resumes servicing broadcast traffic.

When broadcast traffic servicing resumes, the switch begins checking the amount of broadcast traffic against the upper threshold.

Spanning Tree Protocol

Spanning Tree Protocol, as described in the IEEE (Institute of Electrical and Electronic Engineers) 802.1D specification, is a protocol designed to prevent loops within the network topology. A loop can occur if there is more than one path for information to travel between devices. The Spanning Tree Protocol determines the “cost” of a connection. For example, if two devices are connected by two links, spanning tree uses the connection with the lowest cost and blocks the second connection.

Spanning tree prevents loops by allowing only one active path between any two network devices at a time. However, you can also use this protocol to establish redundant links between devices that can take over if the primary link fails.

Backup Path from Client A to Server B: Switch A –> Switch B –> Switch C

	:	3			0
	th			0
a			t:	1
P
		s
		o
	C

Switch A

Switch B
	P
	a
C	th
	:
o	2
s
t:
	2
	0
	0
Path: 1	Switch C
Cost: 100

PC Client A Server B

Primary Path from Client A to Server B: Switch A –> Switch C

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