Allen-Bradley 1783-BMS20CL Industrial Ethernet Switch – Stratix 5700

Allen-Bradley 1783-BMS20CL: Layer 2 Managed Switching Architecture for Deterministic EtherNet/IP Control Networks

The 1783-BMS20CL is a 20-port Layer 2 managed industrial Ethernet switch belonging to Rockwell Automation’s Stratix 5700 series. It is purpose-engineered for plant-floor control networks where deterministic packet delivery, topology redundancy, and deep integration with Logix-based control systems are non-negotiable requirements. Unlike generic IT switches adapted for industrial use, the 1783-BMS20CL is designed from the ground up around the EtherNet/IP CIP (Common Industrial Protocol) communication model, with hardware and firmware features that directly address the latency, jitter, and availability constraints of closed-loop automation.

The port configuration consists of 16 × 10/100BASE-TX copper RJ-45 ports and 4 × 100BASE-FX fiber ports with LC connectors. This hybrid architecture allows engineers to construct mixed copper-fiber ring or star topologies within a single chassis — copper for short-distance panel-to-panel connections and fiber for inter-building or electrically noisy long-distance segments. The fiber ports operate at 100 Mbps full-duplex and support multimode fiber at 1300 nm wavelength, with a maximum segment length of 2 km per link, sufficient for most plant-floor backbone requirements without optical amplification.

Power input accepts 18–32 VDC, centered on the 24 VDC standard used throughout industrial control panels. Dual redundant power input terminals allow connection of two independent 24 VDC supplies; the switch performs automatic failover with no packet loss or reboot cycle, eliminating the power supply as a single point of failure. Total power consumption is approximately 18 W under full port load, well within the thermal budget of standard DIN-rail-mounted control enclosures.

The operating temperature range of 0 °C to +60 °C and storage range of −40 °C to +85 °C, combined with an IP30 enclosure rating and DIN-rail mounting form factor, position the 1783-BMS20CL for deployment inside control cabinets in manufacturing, oil and gas, water treatment, and heavy industry environments. Relative humidity tolerance of 5–95% non-condensing covers the majority of indoor industrial installation scenarios without additional environmental conditioning.

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Technical Parameters

Hardware Logical Analysis

Non-Blocking Switch Fabric: The 1783-BMS20CL implements a store-and-forward switching architecture on a 4.0 Gbps internal backplane. At 20 ports operating at 100 Mbps full-duplex (200 Mbps per port bidirectional), the theoretical maximum aggregate bandwidth demand is 4.0 Gbps — exactly matched by the backplane capacity. This means the switch operates in a non-blocking condition under full simultaneous port utilization, a critical property for EtherNet/IP implicit messaging where I/O data packets must traverse the switch without queuing delay introduced by fabric contention.

Device Level Ring (DLR) Supervisor Capability: The switch supports Rockwell Automation’s Device Level Ring protocol, which provides sub-3 ms ring recovery for topologies of up to 50 nodes. Unlike RSTP (which specifies a maximum convergence time of 1 second), DLR is optimized specifically for EtherNet/IP device rings and achieves fault detection and path switchover within a single PLC scan cycle on most ControlLogix configurations. The 1783-BMS20CL can operate as either a DLR ring supervisor or a ring member, providing topology flexibility without requiring a dedicated supervisor device.

EMC Design and Signal Isolation: The switch chassis employs a grounded steel enclosure with internal PCB-level EMC filtering on all copper port interfaces. Transient voltage suppression (TVS) diodes are placed at each RJ-45 port to clamp ESD events to safe levels before they reach the PHY layer. The fiber ports provide inherent galvanic isolation between network segments — a significant advantage in environments where ground potential differences between control cabinets can corrupt copper-based communications. The 24 VDC power input incorporates an LC filter stage to attenuate conducted emissions from switching power supplies commonly used in industrial panels.

IGMP Snooping and Multicast Traffic Management: EtherNet/IP implicit (I/O) messaging relies heavily on IP multicast for producer-consumer communication between PLCs, drives, and I/O adapters. Without IGMP snooping, multicast frames are flooded to all ports, consuming bandwidth on segments where no consumer exists. The 1783-BMS20CL’s IGMP snooping engine maintains a per-port multicast membership table supporting up to 256 groups, ensuring that multicast I/O data is forwarded only to ports with registered consumers. This directly reduces unnecessary traffic load on field devices with limited Ethernet buffer capacity.

QoS Hardware Queue Architecture: Each port implements 4 hardware egress queues mapped to IEEE 802.1p priority classes. EtherNet/IP implicit I/O traffic is typically marked at DSCP EF (Expedited Forwarding, DSCP 46) or 802.1p priority 6, placing it in the highest-priority queue. This ensures that time-critical I/O data is not delayed by lower-priority traffic such as HMI screen updates, historian data uploads, or SNMP polling — all of which share the same physical network in converged OT/IT architectures.

System Integration Benefits

• Native Studio 5000 Integration: The 1783-BMS20CL appears as a managed device within the Studio 5000 Logix Designer project tree via its EDS (Electronic Data Sheet) file. Engineers can configure port parameters, VLAN assignments, and QoS policies directly from the programming environment without switching to a separate network management console, reducing configuration errors from context switching.
• FactoryTalk Network Manager Compatibility: Full SNMP v3 and RMON 2 support enables integration with Rockwell’s FactoryTalk Network Manager for centralized topology visualization, fault alerting, and configuration backup. Port-level statistics (utilization, error counters, CRC errors) are accessible via standard MIB-II and Cisco private MIBs.
• Deterministic I/O Scan Cycle Support: The combination of non-blocking fabric, hardware QoS queuing, and DLR sub-3 ms recovery ensures that EtherNet/IP implicit I/O connections maintain their requested packet interval (RPI) even during single-fault network events, supporting PLC scan cycles as fast as 1 ms on local ring segments.
• Fiber Backbone for Electrical Noise Immunity: The 4 fiber uplink ports allow the switch to serve as a distribution layer node connected to a fiber backbone, completely eliminating conducted noise coupling between the plant-floor copper segment and the backbone. This is particularly relevant in arc welding, variable frequency drive (VFD), and high-current motor control environments where common-mode noise on copper cables is a documented source of communication faults.
• VLAN Segmentation for OT/IT Convergence: Support for up to 255 active 802.1Q VLANs allows network architects to segment EtherNet/IP device traffic, HMI traffic, historian/SCADA traffic, and IT management traffic onto logically isolated broadcast domains within a single physical switch — reducing broadcast domain size and limiting the blast radius of misconfigured or compromised devices.
• Redundant Power for High-Availability Panels: Dual 24 VDC input terminals with automatic failover allow connection to two independent power rails (e.g., primary UPS-backed supply and secondary panel supply). The failover is hardware-implemented with no software intervention, ensuring continuity of switching function during power supply maintenance or failure without requiring a managed power distribution unit.
• Port-Level Diagnostics via CIP: The switch exposes port status, link state, speed/duplex negotiation results, and error counters as CIP objects readable by the ControlLogix CPU over EtherNet/IP. This allows PLC ladder logic or structured text programs to monitor network health and trigger alarms or safe-state transitions based on network fault conditions — a capability not available with standard IT switches.
• Compact DIN-Rail Form Factor: At approximately 150 × 60 × 120 mm, the 1783-BMS20CL occupies 60 mm of DIN-rail width — equivalent to a standard 3-pole circuit breaker. This allows integration into existing control cabinets without panel redesign, a practical consideration when retrofitting legacy systems with managed networking capability.

Quality Assurance & Global Logistics

Every 1783-BMS20CL unit supplied by siemensplc.com is sourced as genuine Allen-Bradley / Rockwell Automation product. Units are inspected against factory label standards, serial number format verification, and firmware version confirmation prior to dispatch. A 12-month warranty covers hardware failure under normal operating conditions from the date of shipment.

Shipments originate from our warehouse in Xiamen, China — a major export hub with direct access to international freight carriers. Standard export documentation including commercial invoice, packing list, and certificate of origin is provided with every shipment to facilitate customs clearance in destination countries. Available shipping methods include DHL Express (3–5 business days to most destinations), FedEx International Priority, UPS Worldwide Expedited, and sea freight consolidation for bulk orders. In-stock units are dispatched within 1–3 business days of order confirmation. Full cargo insurance is available upon request for high-value consignments.

Export classification: EAR99 (no export license required for most destinations). Buyers in regulated jurisdictions should confirm end-use compliance with applicable export control regulations prior to ordering.

Contact Information

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