Asante Technologies 3624/48 user manual Spanning Tree Algorithm, Spanning Tree Parameters

• Define SNMP Trap Operations

Command	Purpose
snmp trapstation add 192.168.123.100 community public type linkchange	Create a trap host
trap-version 1	192.168.123.100 to which the
	switch can send version 1 link
	change trap messages using
	community string ‘public’.

5.5 Spanning Tree Algorithm

The Spanning Tree Protocol (STP) is part of the IEEE 802.1D standard. It provides for a redundant network without the redundant traffic through closed paths. For example, in a network without spanning tree protocol, the same message will be broadcast through multiple paths, which may start an unending packet-passing cycle. This in turn causes a great amount of extra network traffic, leading to network downtime. The STP reduces a network like this, with multiple, redundant connections, to one in which all points are connected, but where there is only one path between any two points (the connections span the entire network, and the paths are branched, like a tree).

All of the bridges (a switch is a complex bridge) on the network communicate with each other using special packets of data called Bridge Protocol Data Units (BPDUs). The information exchanged in the BPDUs allows the bridges on the network to do the following:

•Elect a single bridge to be the root bridge

•Calculate the shortest path from each bridge to the root bridge

•Select a designated bridge on each segment, which lies closest to the root and forwards all traffic to it

•Select a port on each bridge to forward traffic to the root

•Select the ports on each bridge that forward traffic, and place the redundant ports in blocking states

5.5.1 Spanning Tree Parameters

The operation of the spanning tree algorithm is governed by several parameters.

Forward Time

After a recalculation of the spanning tree, the Forward Time parameter regulates the delay before each port begins transmitting traffic. If a port begins forwarding traffic too soon (before a new root bridge has been selected), the network can be adversely affected. The default value for Forward Time is 15 seconds.

Hello Time

This is the time between BPDUs transmitted by each bridge. The default setting is 2 seconds.

Maximum Age

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