FL SWITCH MM HS(Rapid) Spanning Tree
6874_en_16
PHOENIX CONTACT
5-25
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 attempt to reduce the
reconfiguration times by modifying the timers. However, care should be taken in order to
prevent unstable networks.
Please note that the protocol times are specified by the root switch and that they are
distributed to all devices via BPDU. It is therefore only necessary to modify the values in the
root switch. If the 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
component 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)
≥
MaxAge
–
MaxAge
≥
2 × (Hello Time + 1 s)
The value ((MaxAge/2) - Hello Time) for a ring topology corresponds to the maximum
number of components with active Spanning Tree.
Figure 5-19
Example 1 for the "relevant path"
NOTE:
Modifying the protocol timers may result in unstable networks.
Inactive connection
Relevant path
for setting
the timer values
LNK MODE
1
2
X1
LNK MODE
1
2
X2
LNK MODE
1
2
X3
LNK MODE
1
2
X4
US1
US2
Fail
Reset
MODE
ACT 100
FD
FL SWITCH MM HS
Ord. No. 28 32 32 6
MAC
Address
LNK MODE
1
2
X1
LNK MODE
1
2
X2
LNK MODE
1
2
X3
LNK MODE
1
2
X4
US1
US2
Fail
Reset
MODE
ACT 100
FD
FL SWITCH MM HS
Ord. No. 28 32 32 6
MAC
Address
FL SWITCH MCS 16TX
Ord. No. 28 32 70 0
MAC
Address
1
3
5
7
2
4
6
8
9
11
13
15
10
12
14
16
9
16
10 11 12 13 14 15
1
8
2
3
4
5
6
7
MODE
ACT 100
FD
US1 US2 FAIL
X19
V.24
X17
US1 GND US2 GND
X18
R1 R2
FL SWITCH MCS 16TX
Ord. No. 28 32 70 0
MAC
Address
1
3
5
7
2
4
6
8
9
11
13
15
10
12
14
16
9
16
10 11 12 13 14 15
1
8
2
3
4
5
6
7
MODE
ACT 100
FD
US1 US2 FAIL
X19
V.24
X17
US1 GND US2 GND
X18
R1 R2
FL SWITCH MCS 16TX
Ord. No. 28 32 70 0
MAC
Address
1
3
5
7
2
4
6
8
9
11
13
15
10
12
14
16
9
16
10 11 12 13 14 15
1
8
2
3
4
5
6
7
MODE
ACT 100
FD
US1 US2 FAIL
X19
V.24
X17
US1 GND US2 GND
X18
R1 R2
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