10 — INDUSTRIAL NETWORK TOPOLOGIES

Star, line, ring — and why it matters on the plant floor.

Estimated 8 minutes.

How devices connect — physically.

A topology is the shape of the network — how the cables actually run. The same set of devices can be wired three main ways: star, line, or ring. Each has trade-offs for cost, speed, and reliability.

Star — one switch in the middle.

Every device has its own cable to a central switch.

When to use star.

Star is the default for office networks and many industrial cells. Adding a device is easy — just plug it into a free port. One bad cable affects only one device. The downside: if the switch dies, everyone loses connectivity.

Line — daisy-chain.

Each device passes traffic to the next.

When to use line.

Line topology saves cable. EtherCAT and many Profinet installations use it because devices are physically lined up along a conveyor or a machine. Less switching gear, simpler wiring, but with one big catch.

A cable in a line breaks.

In a line topology of 5 devices, the cable between device 2 and device 3 fails. What happens?

• Only device 3 loses connection
• Devices 3, 4, 5 all lose connection
• Nothing — line topology re-routes

Ring — a closed loop.

Traffic can flow either direction. Lose one cable, the ring still works.

When to use ring.

Rings exist for one reason: redundancy. If a single cable in the ring breaks, the network detects it instantly and re-routes traffic the other way. Most safety-rated and high-availability industrial networks use ring topology with protocols like MRP, HSR, or PRP.

A cable in a ring breaks.

In a 6-device ring, one cable fails. What happens to the network?

• Everything keeps working — traffic re-routes
• The two devices around the break disconnect
• The network goes down for a few seconds, then recovers

Cut a cable. Then another.

Three live networks. Click any cable to cut it. Watch how each topology reacts. Try cutting two cables in the ring.

Brand defaults.

Profinet networks usually run star with a managed switch per cell. EtherCAT runs line — devices daisy-chain by design. Safety and high-availability systems run ring with a redundancy protocol. Knowing the default helps you spot when a design departs from it.

Pick the topology.

You're designing the network for a paint line where 12 devices stretch 50 meters down a conveyor. Cabling cost matters. What's the most natural topology?

• Star — one switch in the middle
• Line — daisy-chain along the conveyor
• Ring — for redundancy

Mix and match.

Real plants combine all three. A ring of switches as the backbone. A star at each switch for local devices. A line for a conveyor or a machine module. The art is matching the topology to what each part of the system actually needs.

One last decision.

A safety system requires "no single cable failure shall stop production." Which topology meets this?

• Star
• Line
• Ring

You can read any plant network diagram.

• Star: central switch. Easy to grow. Switch = single point of failure.
• Line: daisy-chain. Cheapest cable. Any break disconnects downstream.
• Ring: closed loop. Survives one break. Required for safety/HA.
• Real plants combine all three for different parts of the system.

Networking Fundamentals — complete.

• You finished all 10 networking lessons.
• You understand IPs, subnets, MACs, ports, transports, layers, and topologies.
• The free-play Sandbox is now unlocked — build your own network and break it on purpose.