Configuring Advanced

Features

 

 

Configuring Advanced Features

Spanning Tree Protocol (STP)

Spanning Tree Protocol (STP)

 

STP Features

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Feature

Default

Menu

CLI

Web

 

 

 

 

 

 

 

 

 

viewing the STP configuration

n/a

page

page

 

 

 

 

 

9-103

9-105

 

 

 

 

enable/disable STP

disabled

page

page

page

 

 

 

 

9-103

9-106

9-108

 

 

 

reconfiguring general operation

priority: 32768

page

page

 

 

 

 

 

max age: 20 s

9-103

9-106

 

 

 

 

 

hello time: 2 s

 

 

 

 

 

 

 

fwd. delay: 15 s

 

 

 

 

 

 

reconfiguring per-port STP

path cost: var

page

page

 

 

 

 

 

priority: 128

9-103

9-107

 

 

 

 

 

mode: norm

 

 

 

 

 

 

monitoring STP

n/a

page

page

n/a

 

 

 

 

10-15

10-15

 

 

 

 

 

 

 

The switch uses the IEEE 802.1D Spanning Tree Protocol (STP), when

 

enabled, to ensure that only one path at a time is active between any two nodes

 

on the network. In networks where there is more than one physical path

 

between any two nodes, STP ensures a single active path between them by

 

blocking all redundant paths. Enabling STP is necessary in such networks

 

because having more than one path between a pair of nodes causes loops in

 

the network, which can result in duplication of messages, leading to a “broad-

 

cast storm” that can bring down the network.

 

 

 

 

 

 

 

N o t e

You should enable STP in any switch that is part of a redundant physical link

 

(loop topology). (It is recommended that you enable STP on all switches

belonging to a loop topology.) This topic is covered in more detail under “How STP Operates” on page 9-108.

As recommended in the IEEE 802.1Q VLAN standard, the Switches 2512 and 2524 use single-instance STP; a single spanning tree is created to make sure there are no network loops associated with any of the connections to the switch, regardless of whether VLANs are configured on the switch. Thus, these switches do not distinguish between VLANs when identifying redundant physical links. If VLANs are configured on the switch, see “STP Operation with 802.1Q VLANs” on page 9-110.

9-102