Allen-Bradley 1783-BMS20CGN Stratix 5700 Retrofit Switch

Allen-Bradley 1783-BMS20CGN Stratix 5700 Retrofit-Compatible Managed Switch for Legacy Systems

The Allen-Bradley 1783-BMS20CGN is a 20-port managed Ethernet switch from the Stratix 5700 series, engineered by Rockwell Automation for demanding industrial environments. As legacy automation networks age and original equipment reaches end-of-life, the 1783-BMS20CGN has become a critical retrofit component for engineers tasked with modernizing control infrastructure without full system replacement. Whether you are migrating from an older Stratix 5100 unmanaged switch, replacing a discontinued 1783-BMS10CGA, or upgrading a flat network to a segmented, VLAN-capable topology, this switch delivers the performance and compatibility required for a smooth transition.

Designed to integrate seamlessly into existing Allen-Bradley control architectures, the 1783-BMS20CGN supports EtherNet/IP — the standard communication protocol across Rockwell Automation platforms including ControlLogix, CompactLogix, and MicroLogix controllers. This protocol compatibility is essential when retrofitting legacy panels where the PLC program, HMI screens, and I/O addressing must remain intact throughout the migration. Engineers can replace the network layer without rewriting ladder logic or reconfiguring Studio 5000 Logix Designer projects, dramatically reducing downtime risk.

At NINERMAS, we supply the 1783-BMS20CGN with a 12-month warranty, pre-shipment functional testing, and in-stock availability to support urgent retrofit and breakdown replacement scenarios.

Upgrade Compatibility Table

Retrofit Planning for Existing Automation Systems

A successful retrofit using the 1783-BMS20CGN begins well before the switch arrives on-site. The first step is a thorough audit of the existing network topology — documenting every device connected to the legacy switch, including 1756-EN2T EtherNet/IP communication modules, remote I/O adapters such as the 1734-AENT POINT I/O Ethernet adapter, and any PanelView Plus HMI terminals that rely on the network for real-time data exchange. Each of these devices has a fixed IP address and a defined communication path that must be preserved during the switchover.

Power supply capacity is a frequent oversight in retrofit projects. The 1783-BMS20CGN requires a stable 24V DC input, and if the existing 1606-XLP power supply in the control cabinet is already loaded near capacity — powering a 1756-PA75 ControlLogix power supply module, I/O racks, and safety relays — an additional dedicated PSU may be required. Undersized power is one of the most common causes of intermittent communication faults after a network upgrade.

Terminal wiring must be carefully mapped. In older installations, Ethernet cables may be routed through cable trays shared with high-voltage conductors, introducing noise that a managed switch with proper shielding and IGMP filtering can help mitigate. When replacing a flat, unmanaged network, the introduction of VLAN segmentation via the 1783-BMS20CGN allows engineers to isolate motion control traffic — for example, from a Kinetix 5500 servo drive — from standard I/O polling traffic, improving determinism and reducing packet collisions.

Backplane and rack considerations are also relevant when the retrofit extends beyond the network layer. If the project involves replacing a 1756-A17 ControlLogix chassis or adding a new rack to expand I/O capacity, the network switch must be sized to accommodate the additional EtherNet/IP nodes. The 1783-BMS20CGN’s 20-port configuration provides sufficient headroom for most mid-size control system expansions without requiring an additional switch or uplink aggregation.

Communication protocol migration is another key planning element. Sites transitioning from legacy DeviceNet or ControlNet architectures to EtherNet/IP will need to account for scanner module changes — typically replacing a 1756-DNB DeviceNet scanner or 1756-CNB ControlNet bridge with an 1756-EN2T or 1756-EN3TR EtherNet/IP module. The 1783-BMS20CGN is the network backbone that makes this protocol migration possible, providing the managed switching infrastructure that EtherNet/IP requires for reliable, real-time communication.

Programming cable access during commissioning should also be planned. Technicians will need a laptop with RSLinx Classic or FactoryTalk Linx and a standard Ethernet connection to configure the switch’s AOP within Studio 5000, assign VLANs, and verify port mirroring for network diagnostics. Having a 1784-U2DHP USB-to-DH+ programming cable available ensures legacy DH+ devices on the same panel can still be accessed during the transition period.

Downtime Control During System Migration

Minimizing production downtime is the primary concern in any industrial network retrofit. With the 1783-BMS20CGN, the recommended approach is a parallel installation strategy: mount and configure the new switch on the DIN rail alongside the existing unit, pre-configure all VLANs, port assignments, and IP settings, and verify connectivity to a test node before cutting over the live network. This approach allows the entire switchover to be completed in a single planned maintenance window — often under two hours for a 20-node network.

Protecting the original PLC program logic is non-negotiable. Before any hardware change, a full backup of the ControlLogix or CompactLogix project should be saved using Studio 5000 Logix Designer, including all controller tags, I/O configuration trees, and motion group parameters. If the retrofit also involves replacing a 1756-L71 ControlLogix controller or upgrading firmware, the program backup ensures rapid recovery in the event of an unexpected fault during commissioning.

HMI screen continuity must also be verified. PanelView Plus terminals communicate with the PLC via EtherNet/IP, and any IP address change or VLAN reassignment during the retrofit can cause HMI communication faults. Pre-testing the HMI connection through the new switch — using a laptop to simulate the PLC’s IP address — confirms that all screen-to-tag bindings remain intact before the production line is restarted.

Field commissioning should include a structured loop check: verify each I/O point, confirm analog signal integrity from any 1769-IF4 CompactLogix analog input module or similar field device, and run a 30-minute soak test under normal production load before signing off. NINERMAS supplies the 1783-BMS20CGN with pre-shipment functional test documentation, reducing the risk of receiving a faulty unit and ensuring your maintenance window stays on schedule.

Retrofit Support FAQ

Q: Can the 1783-BMS20CGN directly replace a 1783-BMS10CGA without rewiring?
A: In most cases, yes. The 1783-BMS20CGN uses the same 24V DC power input and standard RJ45 Ethernet ports. The primary difference is port count — 20 vs. 10. Existing cables can be reconnected port-by-port. You will need to reconfigure the switch’s IP address and VLAN settings to match your network plan, but no terminal rewiring is typically required.

Q: Is the 1783-BMS20CGN compatible with older ControlLogix L6x series controllers?
A: Yes. The switch communicates via standard EtherNet/IP and is compatible with all Rockwell Automation controllers that support EtherNet/IP, including legacy L61, L62, and L63 ControlLogix processors. The Add-On Profile (AOP) can be imported into RSLogix 5000 v16 and later.

Q: What pre-shipment testing does NINERMAS perform on the 1783-BMS20CGN?
A: Each unit is powered on, port connectivity is verified across all 20 ports, the management interface is confirmed accessible, and the unit is inspected for physical damage. A test report is available upon request. All units ship with a 12-month warranty covering manufacturing defects and functional failures.

Q: How quickly can NINERMAS ship the 1783-BMS20CGN for an emergency breakdown replacement?
A: We maintain in-stock inventory of the 1783-BMS20CGN to support urgent breakdown and retrofit scenarios. Contact our team at sale@ninermas.com or +0086 187 5021 5667 to confirm availability and arrange expedited shipment.