- 3Com Switch Owner Manual

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86 Bridging

Spanning Tree Protocol Entity (STPE)

Introduction The Spanning Tree Protocol Entity (STPE) is part of the PathBuilder S200 series

switch Source Route Bridge functionality. The parameters that control Spanning

Tree Protocol operation are in the Bridge Record and Bridge Link Record. In the

Bridge Record, the STPE Control parameter setting determines whether Automatic

or Manual Spanning Tree is used.

For detailed information about the parameters in the Bridge Record and in the Bridge

Link Record, refer to the “Bridge Parameters” and “Bridge Link Parameters”

sections earlier in this guide.

Automatic

Spanning Tree

Automatic Spanning Tree is dynamic and involves more parameters that enable and

control the Spanning Tree Protocol messages that communicate between the bridges.

By processing these messages, the bridges automatically determine a spanning tree

for the network. These messages are continually updated so the spanning tree

automatically adjusts to the current topology. These messages consume a small

amount of the bandwidth. The automatic version is redundant since PathBuilder

S200 series switch has the capability of re-autocalling the destination, thereby

rerouting over another link.

Manual Spanning

Tree

Manual Spanning Tree is static and cannot adjust to bridge network topology

changes. However, the process is more straightforward and does not consume

network bandwidth (no Hello frames are used). The Spanning Tree is manually

configured on a bridge link basis using the Bridge Link “STPE Link State”

parameter (FORWARD/BLOCK).

What You Need to

Configure

When you configure a node for bridging operation, the spanning tree parameters that

appear on the Bridge Parameters Record and Bridge Link Record depend on whether

you configure manual or automatic spanning tree.

Note

All bridges in a network must operate in the same mode, either all automatic or

all manual.

Custom Software

Key

One Custom Software Key (CSK) enables both the Source Route Bridging and the

Spanning Tree Protocol Entity.

Configuration

STPE Control= AUTO STPE Control = MANUAL

Bridge Record STPE Control = Auto

Bridge Priority

Max Age

Hello Time

Forward Delay

STPE Control = Manual

Bad Hello Threshold

Bad Hello Count

Bridge Link

Record

STPE Priority

STPE Path Cost

STPE Link State