Phoenix Contact FL SWITCH LM 8TX-E - Page 96

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4.2.4.2 Flowchart for specifying the root path
Figure 4-12 Flowchart for specifying the root path
4.2.4.3 Extended configuration
It may be useful to actively specify the topology that is formed due to the Rapid 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 Rapid Spanning Tree Protocol at ports that do
not participate in Rapid Spanning Tree so as to benefit from the fast forwarding function.
The Rapid Spanning Tree Protocol must also be disabled at individual ports if two different
network segments - both using Rapid Spanning Tree - are to be coupled via these ports
without the two tree structures merging into a large Spanning Tree.
Specifying the root switch
The root switch is assigned via the assignment of an appropriate priority for the Rapid
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.
switch Root path
Root path
Yes
Yes
Yes
No
No
No
Determine path to
root switch
Same path costs?
Same priority for switches
(bridge identification)?
Same priority for
individual ports?
Lowest path costs
Root path
Highest priority for
Highest priority for
port Root path
Lowest port number
Path to root switch is determined