User manual

Rapid Spanning Tree

7278_en_01 PHOENIX CONTACT 4-11

4.2.1.8 Flowchart for Specifying the Root Path

Figure 4-10 Flowchart for specifying the root path

4.2.1.9 Extended Configuration

It may be useful to actively specify the topology that is formed due to the Spanning Tree

Protocol and to not leave it to the random MAC addresses of the switches involved.

Non-blocking/blocking data paths can thus be influenced and a load distribution specified.

It may also be useful to explicitly disable the Spanning Tree Protocol at ports that do not

participate in Spanning Tree so as to benefit from the fast forwarding function.

The Spanning Tree Protocol must also be disabled at individual ports if two different

network segments - both using Spanning Tree - are to be coupled via these ports without

the two tree structures melting into a large Spanning Tree.

Specifying the Root Switch

The root switch is assigned via the assignment of an appropriate priority for the Spanning

Tree segment. Set the highest priority (lowest value) in the "Priority" field on the "STP

Bridge Configuration" page in WBM for the switch selected as the root switch. Make sure

that all the other network switches have a lower priority (higher value). Here, the set path

costs are not evaluated.

Specifiy the path

to the root switch

Identical

path costs?

Identical priority of the

switches (bridge identification)?

Identical priority

of the individual ports?

Lowest path costs

root path

Highest priority of the

switch root path

Highest priority of the

port root path

Lowest port number

root path

Path to the

root switch is specified

Ye s

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