One Box, Two Radios: I Moved My Zigbee Network and Added Thread Without Starting Over

SMLIGHT SLZB-MR5U • Zigbee2MQTT • Home Assistant • Matter over Thread

The SMLIGHT SLZB-MR5U with both antennas installed.

Disclosure: SMLIGHT provided the SLZB-MR5U for testing. They did not review or approve this article, and I don’t have an affiliate relationship with them.

I replaced the coordinator of an already-working Zigbee network with the SMLIGHT SLZB-MR5U without re-pairing anything, then used its second radio to add another Thread border router to my existing Google/Nest Thread network. All from one network-connected box.

And the interesting part was what happened after.

I migrated my Zigbee network to the MR5U almost 2 weeks ago, and since then I’ve made several changes. Most of them involved something I had never paid nearly enough attention to before:

Where the damn antenna is.

Why change something that already worked?

I was already using Zigbee2MQTT with Home Assistant and an SMLIGHT SLZB-07 USB coordinator. It was rock solid for my setup.

Because of another testing project, I already had a sensor tracking the average LQI of my Zigbee devices. Before changing anything, my network was sitting pretty consistently above 210 average LQI.

So… why change?

The old network averaged above 210LQI.

One advantage of a network-based coordinator is placement. Instead of needing the Zigbee radio physically attached to the Home Assistant machine, I can put it wherever Ethernet — or, as I eventually discovered, Wi-Fi — can reach.

I’m also learning while writing this article that antenna placement is the beans.

It isn’t something I gave much thought to before. At one point I had Zigbee and Wi-Fi hardware all jammed into the same closet and somehow everything still worked okay.

Eventually I moved the coordinator to my entertainment center, where my internet connection and router now live. The antenna from the old SLZB-07 was basically just poking out from behind the TV.

Old SLZB-07 antenna placement.

MR5U in roughly the same location.

The entertainment-center location. Not exactly an RF laboratory.

Moving Zigbee2MQTT without re-pairing everything

Migrating my existing Zigbee2MQTT network to the MR5U turned out to be pretty painless.

Following Zigbee2MQTT’s adapter migration guide, I recorded the IEEE address from my old coordinator, shut down Zigbee2MQTT, wrote that same address to Radio 1 on the MR5U, and then updated Zigbee2MQTT in Home Assistant so it pointed to the MR5U over the network instead of my old USB adapter.

Because both coordinators use the zstack adapter type, Zigbee2MQTT supports this kind of migration without re-pairing devices.

In other words, I wasn’t creating a new Zigbee network. I was replacing the coordinator hardware underneath the network Zigbee2MQTT already knew.

Writing the old coordinator IEEE address to the MR5U.

Zigbee2MQTT pointed at the MR5U over the network.

It didn’t connect cleanly on my first try. After restarting the MR5U, though, the network came right back.

Every device was still there.

I didn’t re-pair a single one.

If you’re considering doing the same thing, read Zigbee2MQTT’s migration guide first. Not every coordinator-to-coordinator move supports this, and losing a Zigbee network because you skipped five minutes of reading would be a tough one.

Then my numbers got worse

Once the MR5U was running, I started watching my average Zigbee LQI.

And it was lower. A lot lower.

I initially had the MR5U antenna in almost exactly the same location as the old antenna, but my 200+ average dropped below 150 at times.

Here’s the important part, everything still worked.

Lights responded. Sensors reported. Nothing was falling off the network.

My smart home did not care about my pretty statistics, maybe it was just me ☹

The MR5U is also a different physical setup from the single-radio coordinator I was replacing. I now had two radios and two antennas sitting in the same area, with Zigbee and Thread both operating in the 2.4 GHz neighborhood. I’m not going to claim they interfere, but we aren’t comparing apples to apples and it became pretty obvious that orientation and placement were more important than anything else.

So I started messing with the antennas.

After experimenting with orientation and placement, I moved them above the TV and attached them to the wall instead of leaving them hidden behind a giant slab of electronics and metal.

After giving it a few days, the average was back into roughly the 170–180 range and sometimes higher. Much better.

And it reinforced something that seems obvious now. Moving an antenna a foot can matter more than obsessing over a number or a statistic in Home Assistant.

Ethernet is great. But… Wi-Fi?

Then I did something mostly because I’m testing the thing.

I don’t have PoE, so I had been using Ethernet for networking and USB-C for power.

During setup I noticed the MR5U also supports Wi-Fi.

Running your Zigbee coordinator over Wi-Fi sounds a little counterintuitive.

But fudge it. Let’s break something.

I tried it.

I was a little nervous about switching because I had the irrational thought of, “What if I change its network connection and then can’t find it again?”

It was easy.

SMLIGHT’s setup wizard walked me through connecting it to Wi-Fi and gave me the new IP information before I made the switch.

Then I unplugged Ethernet.

Same MR5U. Same Zigbee network.

And the LQI didn’t fall.

In my initial testing, it actually went up. At the time of writing, the average is hovering around 190, and Home Assistant is still seeing the Thread border router normally. I’m going to leave it on Wi-Fi a little longer before I do another victory dance, but so far this has been a pleasant surprise.

LQI after 1 day on Wi-Fi

Granted, the MR5U is only about four feet from my router, not inside of a concrete bunker.

But it opens up another interesting option.

• Want PoE? Use PoE.
• Want Ethernet plus USB power? Do that.
• Have a better antenna location where you really don’t want to run a network cable? Wi-Fi.

Cables? We don’t need no stinkin’ cables.

Well.. except power. One stinkin’ cable.

The MR5U can also be used over USB directly, I didn’t test that configuration but it might be the most stable one of them all, for Zigbee anyway.

Antenna placement using Wi-Fi

The second radio is where things get fun

Moving Zigbee was only half the reason I wanted to test the MR5U.

It has two radios.

Radio 1 was now handling my existing Zigbee2MQTT network, which left Radio 2 available for Thread.

And I already had a Google/Nest Thread network running in my house.

So naturally I started pushing buttons.

Radio 2 set to Thread to remote OTBR.

Testing actual Thread redundancy: The Plug Pull

I tested both ways the MR5U can be used with Thread. Clicking the link next to each toggle provides full instructions.

The setup I liked best was using Radio 2 with Home Assistant’s remote OTBR.

In this configuration, the MR5U radio becomes part of Home Assistant’s OpenThread Border Router setup while using the Thread network I already had rather than creating an entirely separate Thread network.

Home Assistant OpenThread Border Router configured to use the MR5U radio.

Home Assistant then showed both the Home Assistant/OpenThread border router and my Google Nest Hub as border routers on the same Thread network.

Home Assistant showing two border routers on the same Nest Thread network.

Then I unplugged the Nest Hub.

My existing Matter-over-Thread devices kept working.

That was the test I actually cared about.

It’s one thing to see two border routers listed on a screen. It’s another thing to physically pull the plug on one of them and have your Matter devices keep responding.

Thread is designed to support multiple border routers, so removing one border router doesn’t necessarily take the Thread network down with it. In my setup, the MR5U wasn’t just showing up as another border router, it actually kept the network reachable when I removed the Nest Hub from the equation.

That’s cool.

And for me, that’s probably the most convincing demonstration of what Radio 2 adds to this box.

One MR5U, two completely different Thread setups

I also tried running OTBR directly on the MR5U.

That worked too, but it created a separate OpenThread-ESP network.

The alternate mode: OTBR running directly on the MR5U.

My existing Matter-over-Thread devices were already commissioned onto my Nest Thread network. Creating a brand-new Thread network doesn’t magically move the shade onto it.

Home Assistant made the distinction pretty easy to see.

Nest and OpenThread-ESP appear as separate Thread networks.

This is one of those Thread concepts that becomes much easier to understand when you can actually see it happen.

A Thread border router isn’t automatically a border router for the Thread network your devices are already using.

For my house, adding another border router to the Thread network I already had made far more sense than creating another one, so I switched back to the remote OTBR configuration and left it there.

So, was there any reason to replace my old coordinator?

This is the funny part.

My old SLZB-07 worked. It worked really well.

I didn’t need to replace it because Zigbee was broken.

What the MR5U gave me was options.

I moved my existing Zigbee network without re-pairing anything. I gained a second radio that I could use for Thread, adding another controller to my existing network. I tested Ethernet and Wi-Fi. And along the way I learned that where you stick an antenna can matter a whole lot more than I had previously appreciated.

There are probably people who would plug one of these into PoE, mount it somewhere sensible, and never think about it again.

I moved it around the house, stared at LQI numbers, unplugged my Nest Hub, created a second Thread network just to see what would happen, switched the whole thing to Wi-Fi and then sat there waiting to see whether I had broken anything.

So far, I haven’t.

And that’s probably the best compliment I can give this kind of smart home infrastructure. After all of my screwing around, my Zigbee devices are still Zigbee-ing and my Thread devices are still shreading.

One box. Two radios.
And I didn’t have to start over.

More information: SMLIGHT