I am trying to set up a router of a RPi4 plus an LTE modem.
For getting the network available for installing the necessary QMI stuff I need to connect the RPi temporarily to my router, but returning from DHCP to static address on the LAN port fails. This is what I did:
Connect my laptop to LAN port 192.168.1.1
Edit /etc/config/network from static to DHCP
Connect to the RPi to the router
Install the QMI etc packages
Edit /etc/config/network proto back to its original setup
Connect my laptop to LAN port like in step 1. => No network
I also installed Luci and tried to set LAN back to static there, but still I get no connection.
In phase 2. commented the rest of the lines except eth0 and proto that I changed from static to dhcp. That worked fine, and I could connect through the router.
In phase 5. I removed the #'s and changed dhcp back to static, exactly the original config, but no go.
If you click on the small drop down of the Luci save&apply button (to the right hand side of the button), you see an "apply unchecked". But use it with care.
But you cannot change the ip of the device with luci other than using apply unchecked, it will always rollback the changes...