I'm having a super weird problem ............

I have a router which i have set up myself and i have sims from 2 LTE ISP's that i can swap (while also changing the APN using profiles) (i got sick and tired of getting told by the ISP to put the sim into a phone for an hr to fix problems with the fixed LTE provider)

The router is configured with DHCP and it works perfectly fine and swapping the sim doesnt change those settings. So the weird thing is: after turning the router off and swapping the sim, I am unable to log into the router to change the APN. Both windows and linux do not accept/receive DHCP config after the sim is swapped when no changes have been made to the router. Theoretically the internal network structure hasnt changed either but for some reason the hard wired lines wont DHCP while wifi connections still work fine.

This situation has occurred three times now, so its not a once off.

In this latest snafu, after swapping back to the original sim, all of a sudden the the wifi units would no longer access the router, but their wifi connections worked well enough to enable internet access and the lined computers could suddenly log into the router.

Why/how are the DHCP settings (internal IP's) affected when nothing changes in the router control when the external IP changes?