Moxa Technologies EtherDevice User Manual page 78

Configuration Limits
We should point out that the Spanning Tree Algorithm places certain limits on three of the
configuration items described above:
[Eq. 1]:
[Eq. 2]:
[Eq. 3]:
These three variables are further restricted by the following two inequalities:
[Eq. 4]:
MOXA EtherDevice Server's firmware will alert you immediately if any of these
restrictions are violated. For example, setting
Hello Time = 5 sec, Max. Age = 20 sec, and Forwarding Delay = 4 sec does not violate Eqs.
1 through 3, but does violate Eq. 4, since in this case,
2 * (Hello Time – 1 sec) = 8 sec, and 2 * (Forwarding Delay – 1 sec) = 6 sec.
You can remedy the situation in any number of ways. One solution is to simply increase the
Forwarding Delay value to at least 11 sec.
NOTE If you Enable "Redundant Ring quick setup" and then later Disable it, you must Disable
STP for ports 7 and 8 to disable this device as a Spanning Tree node.
6-28 MOXA EtherDevice Server User's Manual
1 sec ≦ Hello Time ≦ 10 sec
6 sec ≦ Max. Age ≦ 40 sec
4 sec ≦ Forwarding Delay ≦ 30 sec
2 * (Hello Time – 1 sec) ≦ Max. Age ≦ 2 * (Forwarding Delay – 1 sec)