Allen-Bradley 1756-CNBR/D ControlNet Communications Bridge | Replacement, Equivalent & Selection Guide
The Allen-Bradley 1756-CNBR/D is a ControlNet Communications Bridge module for the ControlLogix platform, Series D revision. It enables seamless bridging between ControlNet networks, allowing multi-network topologies in large-scale industrial automation systems. This page provides full technical specifications, compatible replacement options, application guidance, and sourcing information to help engineers and procurement teams make confident decisions.
Technical Specifications
- Manufacturer: Allen-Bradley / Rockwell Automation
- Part Number: 1756-CNBR/D
- Series: D
- Platform: ControlLogix (1756 Chassis)
- Network: ControlNet (IEEE 802.3 coax / fiber)
- Function: ControlNet-to-ControlNet Bridge
- Ports: Dual BNC (coaxial) ControlNet ports
- Backplane Communication: ControlLogix backplane
- Power Consumption: ~4.5 W (from chassis backplane)
- Operating Temperature: 0 °C to 60 °C
- Storage Temperature: −40 °C to 85 °C
- Humidity: 5–95% non-condensing
- Certifications: UL, CE, cUL
- Firmware: Upgradeable via RSLogix 5000 / Studio 5000
- Weight: Approx. 200 g
Compatible Replacement & Equivalent Models
When the 1756-CNBR/D is unavailable or end-of-life, the following alternatives may be considered depending on your network architecture and firmware requirements:
- 1756-CNBR/B & /C — Earlier series revisions; functionally equivalent but may require firmware alignment. Suitable for legacy systems.
- 1756-CN2/A, /B — ControlNet Scanner/Bridge with enhanced diagnostics; direct functional replacement in most topologies.
- 1756-CN2R/A — Redundant ControlNet interface; recommended upgrade path for high-availability systems.
- 1756-CN2RXT — Extended-temperature variant for harsh environments (−25 °C to 70 °C).
- 1756-ENBT / 1756-EN2T — EtherNet/IP bridge modules; applicable if migrating from ControlNet to Ethernet topology.
Note: Always verify firmware compatibility and chassis slot requirements before substituting modules. Contact Konmask.com for pre-sales compatibility verification.
Why Choose the Original 1756-CNBR/D
- Proven Series D Reliability: Series D incorporates hardware and firmware refinements over earlier revisions, reducing field failure rates.
- Deterministic ControlNet Performance: Guaranteed scheduled data delivery critical for motion control and safety-adjacent applications.
- Native ControlLogix Integration: Zero-configuration backplane communication with ControlLogix CPUs (e.g., 1756-L6x, 1756-L7x, 1756-L8x).
- Long Installed Base: Extensive RSLogix/Studio 5000 EDS support and field documentation available.
- Dual-Media Redundancy Support: Coaxial A/B media redundancy for network fault tolerance.
Typical Applications
- Automotive assembly line control networks
- Oil & gas distributed control systems (DCS) with ControlNet backbone
- Water/wastewater treatment plant SCADA integration
- Food & beverage processing with multi-zone PLC networks
- Power generation and utilities substation automation
- Pharmaceutical batch control systems (FDA 21 CFR Part 11 environments)
- Mining and materials handling conveyor control
System Compatibility
- Chassis: All 1756 ControlLogix chassis (4, 7, 10, 13, 17-slot)
- Power Supplies: 1756-PA72, 1756-PB72, 1756-PA75, 1756-PB75 and compatible variants
- CPUs: 1756-L55, 1756-L6x, 1756-L7x, 1756-L8x series
- Software: RSLogix 5000 v13+, Studio 5000 Logix Designer v21+
- Network Topology: Linear, star (with repeaters), and redundant media ControlNet
- Coexistence: Compatible with 1756-CNB, 1756-CNBR, and 1756-CN2 modules on the same network
Selection Guide
| Requirement | Recommended Model |
|---|---|
| Standard ControlNet bridge, Series D | 1756-CNBR/D (this product) |
| Redundant ControlNet interface needed | 1756-CN2R/A |
| Extended temperature environment | 1756-CN2RXT |
| Migrating to EtherNet/IP | 1756-EN2T or 1756-ENBT |
| Legacy system, budget-constrained | 1756-CNBR/B or /C (refurbished) |
| High-availability process control | 1756-CN2R/A with redundant chassis |
Quality Assurance & Sourcing
- Inspection: All units undergo visual inspection, functional power-on testing, and firmware version verification prior to shipment.
- Condition: New surplus, refurbished (tested), or factory-new stock available — specify at time of order.
- Traceability: Batch and serial number documentation provided on request.
- Packaging: ESD-safe anti-static packaging; original OEM packaging where available.
- Warranty: 12-month Konmask warranty on all tested units; OEM warranty on factory-new stock.
- Lead Time: In-stock items ship within 1–3 business days; sourced items 5–15 business days.
How to Order
- Confirm your chassis series and available slot count.
- Verify current firmware version of your ControlLogix CPU (RSLogix/Studio 5000).
- Specify required condition: new surplus / refurbished / factory-new.
- Contact Konmask.com with your PO or RFQ — include quantity, delivery address, and any certification requirements.
- Receive order confirmation with lead time and tracking within 24 business hours.
📧 support@konmask.com | 📞 +0086 19859288691
Replacement & Compatibility FAQ
Q: Can I replace a 1756-CNBR/B with a 1756-CNBR/D without reconfiguring RSLogix?
A: In most cases yes — the Series D is backward-compatible. However, a firmware update on the CPU may be required. Always perform a test in a non-production environment first.
Q: Is the 1756-CNBR/D still in production?
A: Rockwell Automation has transitioned newer installations to the 1756-CN2 family. The CNBR/D remains available as new surplus and refurbished stock through authorized distributors like Konmask.com.
Q: Can this module bridge ControlNet to EtherNet/IP?
A: No. The 1756-CNBR/D bridges ControlNet-to-ControlNet only. For ControlNet-to-EtherNet/IP bridging, consider the 1756-EN2T with appropriate routing configuration.
Q: What is the maximum number of nodes supported per ControlNet segment?
A: ControlNet supports up to 99 nodes per segment (addresses 1–99). The bridge itself occupies one node address on each connected segment.
Q: Do you provide test reports or certificates of conformance?
A: Yes. Certificates of conformance and functional test reports are available upon request for all refurbished units.
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Contact: support@konmask.com | +0086 19859288691
