I recently set up a new internet connection at home and my modem didn't support bridge mode. Instead I had to use an option called "IP Passthrough". Here's some details on that modem configuration. I've never heard of IP Passthrough before, and there's not much technical information about it in particular.
Here's the physical details of my modem:
[WAN] - Connected fiber or DSL (PPPoE) [LAN0] - Connected to my router with public IP assigned [LAN1] - \ [LAN2] - -> LAN 1-3 Still receive DHCP with NAT [LAN3] - /
So what exactly - in non consumer terminology :) - is "IP Passthrough" doing under the hood to provision my public IP address on my router, while also using the same public IP for itself? Is this Proxy ARP or similar?
Another thing referenced in that reddit thread is "DHCPS-fixed". I've never heard of this either, and it doesn't seem the same as a DHCP Relay.
DHCPS-fixed seems to work best as it allows you to specify the MAC address of the device to pass traffic through to. It is worth mentioning that this is still a DHCP address that your internal device is getting
It'd be great to get a better understanding of these terms and learn how these methods work. Thanks!