Quick Look | Core Value of R-NAT

· Single-Chip Standalone Networking: Natively implements NAT forwarding, DHCP service, and DNS proxy — core LAN services — on a resource-constrained RTOS SoC

· Unified Multi-Interface Management: Wi-Fi, Ethernet, and USB ECM interfaces are managed under a single framework, with WAN/LAN roles flexibly configurable

· More Reliable Connectivity: Supports automatic priority-based multi-WAN switchover, plus subnet conflict detection and self-healing

In traditional architectures, cross-interface networking on edge devices is typically implemented through Layer-2 bridging, leaving the device permanently dependent on the upstream network and unable to manage its own LAN. Achieving full subnet segmentation, address allocation, and packet forwarding usually requires introducing a more capable platform, which drives up hardware cost and complexity.

Realtek's newly released Ameba Wi-Fi R-NAT solution natively integrates Layer-3 networking capability into a resource-constrained RTOS SoC — consolidating NAT address translation, DHCP service, and multi-link management into a single Ameba chip. This turns the end device from a mere "extension of the upstream network" into a "network node with independent networking capability," enabling cross-interface data forwarding and LAN management without switching to a higher-end platform.

What Is R-NAT?

R-NAT is a lightweight network routing and bridging middleware that runs on the Ameba RTOS platform. Built on the LwIP stack, R-NAT abstracts physical interfaces such as Wi-Fi, Ethernet, and USB ECM into unified LwIP netif instances, and assigns each one a WAN (upstream wide-area network) or LAN (downstream local-area network) routing role, forming a complete network forwarding and control mechanism.

Typical R-NAT Use Cases

Ameba devices can be directly deployed in the following typical end-product network topologies:

Scenario 1: Wi-Fi Router

The Ameba device connects to the upstream network via Wi-Fi STA. Downstream devices can access the internet through the SoftAP hotspot, Ethernet port, or USB-ECM interface that the Ameba device provides, achieving extended signal coverage and shared uplink access for multiple devices — the entire solution runs on a single chip — with no additional routing hardware required.

Scenario 2: Wired-to-Wireless Hotspot

The Ameba device connects to the upstream broadband network via Ethernet or USB-ECM, and uses SoftAP to convert wired traffic into a Wi-Fi hotspot for mobile devices to join. A typical application is converting an industrial Ethernet connection into a wireless access point, letting multiple mobile devices share internet access nearby.

Scenario 3: 4G Router

The Ameba device connects to a 4G/5G modem via USB Host, using USB ECM as the upstream WAN to obtain cellular network access, while simultaneously enabling SoftAP to provide access for downstream terminals. R-NAT performs address allocation and transparent forwarding on the device side, letting phones, PCs, and other terminals share the cellular connection, making it ideal for outdoor, in-vehicle, or temporary deployments without fixed broadband.

What Capabilities Does R-NAT Offer?

Unified Multi-Interface Management

Physical interfaces such as Wi-Fi (STA/SoftAP), Ethernet, and USB ECM are all brought under the unified R-NAT framework. Each interface can independently configure its IP acquisition method and routing role, flexibly supporting network topologies such as Wi-Fi routers and wired-to-wireless APs.

Dynamic Multi-WAN Priority Switching

Multiple WAN interfaces (such as Wi-Fi STA and Ethernet) can be online at the same time. The system always routes through the highest-priority active interface by default; whenever a WAN link's status changes (e.g., disconnection, or a cable being plugged/unplugged), the system automatically switches routes to keep connectivity continuously available.

Automatic Subnet Conflict Detection and Self-Healing

During LAN interface initialization and whenever a WAN interface obtains a new IP, R-NAT automatically checks for subnet conflicts. If an overlapping subnet is detected, the system automatically reassigns IP addresses and restarts the DHCP service, completing network self-healing with no manual intervention required.

Transparent NAT Forwarding

Multiple downstream LAN devices share the same WAN public IP to access the internet through NAT address translation. IP address and port translation for each packet is handled automatically at the underlying layer, making the entire forwarding process completely transparent to downstream terminals.

DNS Proxy and Independent Multi-Channel DHCP

Each LAN interface runs its own independent DHCP server instance, assigning IP address, gateway, and DNS information to connected terminals, with the DHCP service on each LAN interface fully isolated from the others. In addition, a built-in DNS proxy forwards LAN-side queries through the gateway to the upstream WAN-side server, automatically syncing resolution state whenever the WAN interface's IP changes — ensuring LAN infrastructure services remain continuously available.

Recommended R-NAT SoC: RTL8721F

The RTL8721F meets, at the hardware level, the dual requirements of multi-interface routing — both "interfaces" and "compute power."

Dual-Core Processor: Equipped with a dual-core Real-M300 processor (compatible with the Arm Cortex®-M55 ISA), providing the compute power needed for network stack processing, forwarding-path scheduling, and NAT mapping maintenance.
Dual-Band Wi-Fi 6 with MCC Architecture: Supports 2.4GHz/5GHz dual-band Wi-Fi 6 along with MCC (Multi-Channel Concurrent) operation, effectively reducing channel interference during relaying and concurrent forwarding to ensure link stability.
Full-Featured High-Speed Peripheral Interfaces: Natively integrates an Ethernet port, high-speed USB 2.0 (supporting Host/Device modes and the ECM protocol), SDIO, and a CAN bus, providing the complete physical-layer support required for multi-interface routing and forwarding.

The latest Ameba SDK, including the R-NAT middleware source code, is now officially available — developers are welcome to download and evaluate it!

📄 View the R-NAT Development Guide

📥 Download the Latest SDK