Ring topology – Rockwell Automation 1786-series ControlNet Fiber Media Planning and Installation Guide User Manual

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Rockwell Automation Publication CNET-IN001C-EN-P - October 2011

Chapter 1 Get Started with the ControlNet Network Fiber Media System

Ring Topology

A ring topology provides redundancy by providing two data paths in a single ring.
A ring can sustain two faults before that data connection is lost. You should
consider a ring when your devices (Controller and I/O) are single port (A only)
and media redundancy is required. Only the 1786-RPFRL and 1786-RPFRXL
repeater modules support ring topologies.

In a ring topology on the ControlNet network, you can use:

• Up to 5 repeaters by using one 1786-RPA/A repeater adapter.
• The 1786-RPA/B repeater adapter allows for a maximum of 20

1786-RPFRL (long distance) or 1786-RPFRL/X (extra long-distance)
ring repeaters.

Figure 4 - Ring Topology

If a ring is broken, the configuration then becomes a linear bus and the number of
repeaters in SERIES depends on where the ring is broken. You will have as many
repeaters as in the original ring.

See

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to determine different topology constraints.

Up to 20 1786-RPFR(X)L
repeaters on a fiber ring.

Fib

Fiber

Fibe

Fiber

Fib

Node(s)

RPA +
RPFRXL

Coax

Coax Network