You may want to split this experiment across two sdcards. One for the rpi access point (call it rpiAP) and one for your app. Only then figure out how to merge one into the other.
The conventional way to add a dhcp/dns to your intranet without affecting the existing one is either to make rpiAP serve a different subnet then use nat on the rpiAP to funnel wireless traffic down the rpiAP ethernet or have rpiAP forward its requests to the existing dhcp/dns for same subnet down the rpiAP ethernet. Typically the rpiAP ethernet is a fixed address on the intranet subnet.
At home the second method is fine because rpiAP will have its ethernet plugged into your intranet. Won't work out in the field. You're stuck with using the first method because rpiAP is going to have to have its own dhcp/dns server.
Now here comes the horrible fudge. It's very common for isp router dhcp/dns to be on 192.168.1.0/24. You could make rpiAP sit on 192.168.2.0/30 thus when out in the field when you connect to it with your phone you will know the S30 must be the other ip address. Or.. and this is something I know nothing about, plug your phone into the rpiAP ethernet, possibly yielding possibility to allow phone tethering to work?
You'll have to read up on subnets yourself. As a starter the "/24" or "/30" above specifies the subnet range. It's easier to understand when written out as a lengthy binary number. In any subnet, all bits lo and all bits hi are reserved which is why "/30" only yields two usable ip addresses. I'm rusty. Should I have written 192.168.2.0/30 as 192.168.2.252/30?
If you disable NetworkManager and follow (eg: dhcpcd/bind) tutorial you'll be able to tell 'dhcpcd' to assign fixed address to mac address for your S30.
Hopefully sdm (or maybe even pihole) can help. Not used pihole either! You can run dhcp/dns on a toaster. You only need enough grunt to run your app.
The problem is too many unknowns.![;-)]( "Wink")
The conventional way to add a dhcp/dns to your intranet without affecting the existing one is either to make rpiAP serve a different subnet then use nat on the rpiAP to funnel wireless traffic down the rpiAP ethernet or have rpiAP forward its requests to the existing dhcp/dns for same subnet down the rpiAP ethernet. Typically the rpiAP ethernet is a fixed address on the intranet subnet.
At home the second method is fine because rpiAP will have its ethernet plugged into your intranet. Won't work out in the field. You're stuck with using the first method because rpiAP is going to have to have its own dhcp/dns server.
Now here comes the horrible fudge. It's very common for isp router dhcp/dns to be on 192.168.1.0/24. You could make rpiAP sit on 192.168.2.0/30 thus when out in the field when you connect to it with your phone you will know the S30 must be the other ip address. Or.. and this is something I know nothing about, plug your phone into the rpiAP ethernet, possibly yielding possibility to allow phone tethering to work?
You'll have to read up on subnets yourself. As a starter the "/24" or "/30" above specifies the subnet range. It's easier to understand when written out as a lengthy binary number. In any subnet, all bits lo and all bits hi are reserved which is why "/30" only yields two usable ip addresses. I'm rusty. Should I have written 192.168.2.0/30 as 192.168.2.252/30?
If you disable NetworkManager and follow (eg: dhcpcd/bind) tutorial you'll be able to tell 'dhcpcd' to assign fixed address to mac address for your S30.
Hopefully sdm (or maybe even pihole) can help. Not used pihole either! You can run dhcp/dns on a toaster. You only need enough grunt to run your app.
The problem is too many unknowns.
Statistics: Posted by swampdog — Tue Aug 26, 2025 4:41 pm