There is a detail about Shelly devices many people do not know: as well as joining your Wi-Fi as a client, they can broadcast a network of their own. And if one device can broadcast a network, another can join it.
That opens up two possibilities using hardware already on the installation, with no repeater to buy: reaching a corner with poor coverage, and keeping control of the devices when the main network goes down.
The arrangement
Two devices, with different jobs:
- Device A sits in good coverage, connected to your router, with access point mode switched on. It broadcasts a network of its own.
- Device B is further away, on a marginal or intermittent signal. It has two networks configured: the house’s main one and, as secondary, the one A broadcasts.
B always tries the main network first. If it cannot find it, it moves to A’s network by itself and stays operational.
Setting it up
On device A, open its web interface and find the Wi-Fi mode settings. There you enable access point mode and set the network name and password it will broadcast. Write both down: you need them for the next step.
On device B, in its Wi-Fi settings, add both networks: the main one first and A’s as secondary. Do this with B near A while you configure, and take it to its final position afterwards.
If you are doing this on an installation with several devices, provisioning them as a batch first with the SIT-IoT app saves the tedious part: they all join the main network with their static IP in one pass, and then you only touch the two that will act as A and B.
What it actually solves, and what it does not
It pays to be precise here, because it is easy to expect more of this than it gives.
It does solve range. A device at the edge of coverage — the one in the cellar, on the terrace, at the back of the garage — stops depending on a marginal signal.
It does keep local control when the router restarts or hangs. Automations between devices and access from inside the house carry on working.
It does not replace internet. And this is the part to understand before selling the arrangement to a client: if what has gone down is the house’s connection, the backup network does not give you back remote access or cloud notifications. Device A is connected to a router with no way out. What you gain is control inside the installation, not from outside it.
Put another way: it is a backup for the local network, not for connectivity. Knowing that, it remains genuinely useful; expecting otherwise, it disappoints.
Proving the backup works
A backup nobody has tested is not a backup. The test is simple and worth doing: switch the main router off and check that device B still answers. If it does, it has moved onto A’s network.
What is less simple is catching the silent failure: B not holding the secondary network properly and sitting disconnected for weeks without anyone noticing, right up until the day it was needed.
In the console, the last seen column is what watches that without effort. A device that ought to be permanently online and has not reported for days is a fault that has not shown itself yet. On an installation handed over to a client, that periodic glance is the difference between finding it yourself and being told about it.
When this is not the answer
If coverage is poor across half the house, this is a patch. A proper access point deals with the underlying problem better, and the devices appreciate a steady signal far more than an alternative to fall back on.
And remember the basics before assuming the problem is range: these devices only see the 2.4 GHz band, they need WPA2 as a minimum, and they do better on a fixed channel of 1, 6 or 11. Plenty of “dead spots” turn out to be a router publishing both bands under one name.
The arrangement works with Gen2, Gen3 and Gen4 devices, as do the app and the console. The app is on Google Play: SIT-IoT Smart Installer Tool.