Using a Pi3 for an isolated IoT network

Hey! I am interested in running OpenWrt on a Pie 3b+ so I can isolate my IOT devices. I will also run MQTT on the Pi and Homeassistant on a more powerful machine. The problem is I cannot connect to the wifi network after reboot.

the eth0 is for upstream/"wan" and the phy0 for the pseudo-lan of the IOT devices.
The wan would actually be my home lan.

I disabled bridges. eth0 is assiged to wan rules, DHCP client. phy0 has static IP and DHCP server.

I have to ssh into the Pi running OpenWrt via eth0 and do a service network restart and then I can connect to the wifi..

Any ideeas what is wrong with it?

The RPi4/ RPi5 can be very capable and fast wired-only routers. However the RPi3 is hampered by its USB2 system bus, which makes it slow and overpriced compared to more traditional plastic routers running OpenWrt.

The wireless capabilities of all RPi generations are very limited and slow, which makes them badly suited for AP tasks.

A router should be a router only, any additional server tasks just increase its attack surface and make the configuration more complex.

Thanks for your concerns, it will be isolated into my lan and i don't need high bandwidth, it will only serve some tasmota devices and other iot devices wich I want to block anyway so they dont call home (PRC shit.)

Any advice about my real issue? with the wifi working only after restarting the networking service? Thanks!

I have had this same issue for long time but with a different device, in my case, dnsmasq wasn't running at device bootup. Just couldn't figure out why it wasn't running. Restarting the network also causes dnsmasq to start again. So please confirm this whether it's the same case with you. So next time it happens, instead of restarting network, start dnsmasq and see if you're able to connect to wifi.

I added this line in rc.local
sleep 15; /etc/init.d/dnsmasq start, and it fixed the issue for me.

I strongly believe it's the onboard WiFi issue, Broadcom doesn't play nice with OpenWrt in many cases, I do have an old RPi 3B, for a small corner I am currently using it with extra MT7610U USB 802.11ac WiFi dongle, it hides in my ceiling for ~40 days already and no problem at all (and it can saturate 100M LAN speed with ~5 clients most of the time). With RPi 4B I am also getting lots of trouble with it's onboard WiFi so I will only try to use it as client only.

Thanks, Alpha1096!
In my case, wasn't dnsmasq the culprit, but the wapd service.
I added to the rc.local a line to restart the service and now it works.

It gets started at boot time, but something happens to the interface and wapd has to be restarted to work...

Thanks again!