EOTec 2104 User Manual
Advanced Features of Switch Tools
Modbus Diagnostics Example
As an example of how to debug a network using the Modbus registers, we will examine
a simple ring topology.
Scenario 1: No Breaks
The diagram below depicts three EOTec 2104 Ethernet Ring Switches configured for
one ring. The ring network is currently in good health (no breaks in the ring) with the
solid line indicating the active part of the ring, and the dashed line indicating the standby
(blocked) part of the ring.
Because the ring network is in good health, we can expect these values from the
Modbus registers of each switch:
Switch A
Switch B
Switch C
Ring 1 Complete:
1
Ring 1 Complete:
1
Ring 1 Complete:
1
First Port of Ring 1:
1
First Port of Ring 1:
1
First Port of Ring 1:
0
Second Port of Ring 1:
1
Second Port of Ring 1:
1
Second Port of Ring 1:
1
A ring network in good health would have the Ring Complete bit set to one in all ring
switches. Also, all ports in the ring should be forwarding except for one port that should
be blocking. The blocking port indicates the standby/backup path of the existing ring.
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