SMLIGHT, the maker of the SLZB Zigbee coordinators, announced ZREL on 23 October 2026. It is a pair of small boards that pick up raw Zigbee radio traffic at one end, send it over a LAN cable and put it back on the air at the other end. The aim is to stretch one existing Zigbee network to a detached garage, another floor or a basement without chaining routers through concrete and without running a second coordinator there.

How the pair works

You need two units, and each one takes a role. The Master sits inside your current Zigbee coverage, and the Remote goes where the signal does not reach. Both join your network as ordinary Zigbee routers, so the coordinator, ZHA or Zigbee2MQTT and the device list stay as they are. The network keeps one PAN ID, one channel and one network key. Devices near the Remote pair the usual way and link to the Remote by radio.

Between the units runs a TCP connection on port 6600. Whatever the Remote's radio hears, the Master transmits, and the other way round. SMLIGHT says the coordinator only sees two routers and has no idea that the hop between them is a cable. Port 6601 is used for management and UDP port 6602 for discovery.

SMLIGHT describes ZREL as the first device that carries raw Zigbee radio traffic over Ethernet.

Hardware

Each board has a Silicon Labs EFR32MG24 radio, a WIZnet W5500 Ethernet controller with hardware TCP/IP and an external antenna. There is no serial link inside, because the radio chip drives the W5500 directly. Power comes over PoE or USB-C. The units get an address by DHCP or a static IP, and the Remote finds the Master automatically within one LAN segment. Across segments you enter the Master's IP by hand. SMLIGHT says the link should run over a cable, not Wi-Fi.

Setup goes through ZREL Config, a desktop app and command-line tool for Windows, macOS and Linux. You set one unit as the Master (Server mode) and the other as the Remote (Client mode), allow joining on the coordinator and press "Search & Join Network" on each. The app also shows network state, transmit power (up to +20 dBm), tunnel counters and live device logs.

Latency

The launch post refers to an SMLIGHT test from September. It compared two of its EFR32MG24 coordinators at 115200 baud: the SLZB-07Mg24 over USB and the SLZB-06Mg24U over wired Ethernet. The Ethernet one had a lower average round-trip time at every payload size, 12.3 ms against 19.0 ms on average, or about 35% less. That test measured the path between the host and the coordinator, not ZREL itself and not the Zigbee radio link.

Price and availability

The first batch is limited and ships as a bare board with its antenna, with no case. SMLIGHT offers a free STL file for a 3D-printed enclosure. The launch price is $25 per unit until the batch sells out, and a working setup needs two units. The regular price will be $36 to $40 per unit, with an enclosure. ZREL is sold on AliExpress and smartlight.me, and local distributors are to follow.