User Documentation

User Manual Managed Switches
80
NOTE: We suggest not enabling the Spanning Tree Protocol once the port is connected to a device
(PLC, RTU, etc.) as opposed to network equipment. The reason is that it will cause unnecessary
negotiation.
Edge Port
Setting
Description
Factory Default
Auto
1. If the port does not receive a BPDU within 3
seconds, the port will be in the forwarding state.
2. Once the port receives a BPDU, it will start the
RSTP negotiation process.
Auto
Force Edge
The port is fixed as an edge port and will always be in the
forwarding state
False
The port is set as the normal RSTP port
Port Priority
Setting
Description
Factory Default
Numerical value
selected by user
Increase this port’s priority as a node on the Spanning
Tree topology by entering a lower number.
128
Port Cost
Setting
Description
Factory Default
Numerical value
input by user
Input a higher cost to indicate that this port is less suitable
as a node for the Spanning Tree topology.
200000
Port Status
It indicates the current Spanning Tree status of this port. “Forwarding” for normal transmission, or
“Blocking” to block transmission.
Configuration Limits of STP/RSTP
The Spanning Tree Algorithm places limits on three of the configuration items described previously:
Rule/Limitation 1: 1 sec ≦ Hello Time ≦ 10 sec
Rule/Limitation 2: 6 sec ≦ Max. Age ≦ 40 sec
Rule/Limitation 3: 4 sec ≦ Forwarding Delay ≦ 30 sec
These three variables are further restricted by the following two inequalities:
Rule/Limitation 4: 2 x (Hello Time + 1 sec) ≦ Max. Age ≦ 2 x (Forwarding Delay – 1 sec)
The firmware will alert you immediately if any of these restrictions are violated.
For example, setting Hello Time = 5 sec and
Max. Age = 20 sec and
Forwarding Delay = 4 sec
does not violate rule 1 through 3, but does violate rule 4 because in this case
2 x (Hello Time + 1 sec) = 12 sec and