Guest network for IoT

I have router TP-LINK Archer C6 which doesn’t support VLAN. The good news is that at least Guest Network is supported.

  1. Is it possible and safe to put all IoT devices to Guest Network and using ‘Main Network’ for personal devices?
  2. Another way is that I could also plug in my old router into current Archer C6 and then maybe it will be correctly separated?

Sorry for newbie questions but I would like to start my adventure with HA safely.

The configuration options for that TP-Link router are very limited. Putting IoT devices onto a separate WiFi network is a good idea, until you would then need to communicate with those devices. Maybe it works without allowing access from the guest network into your main network, but if not, then you may need to open up access from the guest network into the main network which makes the separation less useful.
Also, what you normally want to do is to cut off IoT devices from “calling home”, i.e. restricting their Internet access, which does not seem to be possible on that TP-Link router.

There is a good 3-part series about building a secure and reliable network including VLANs, starting here: https://youtu.be/ufJ3dPAgFiM