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Smart Managed Compact Switch
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PHOENIX CONTACT 8089_en_03
5.2.5.9 Modifying the protocol timers
It may be necessary to modify the protocol timers if, e.g., there are more than ten active
Spanning Tree components in a single network. You can also try to reduce the reconfigura-
tion times by modifying the timers. However, care should be taken in order to prevent unsta-
ble networks.
Please note that the protocol times are specified by the root switch and that they are distrib-
uted to all devices via BPDU. It is therefore necessary to modify the values in the root switch
at first. If a root switch fails, the timer values of another active STP switch (i.e., the new root
switch) will be valid for the entire network segment. Please remember this during compo-
nent configuration.
Specifying the timer values (STP and RSTP)
–
Maximum number of active Spanning Tree components along the path beginning at the
root switch (please refer to the following two example illustrations):
= (MaxAge / 2) - Hello Time + 1
– 2 x (Forward Delay - 1 s)
³
MaxAge
– MaxAge ³ 2 × (Hel 1 s)
The value ((MaxAge / 2) - Hello Time) for a ring topology corresponds to the maximum num-
ber of components with active Spanning Tree.
Figure 5-17 Example 1 of the “relevant path”
Modifying the protocol timers may result in unstable networks.