I have an Arris TG1682G straight from my ISP, which is Spectrum. It's a cable modem/router that I have configured to bridged mode. Then, I have a D-Link DIR-645 that's connected to it. It works fine while on default firmware. But as soon as I upload the OpenWRT firmware to my D-Link router, I lose all connections. Any ideas as to why this is? I'm very new to this whole thing.
I'm going to guess that they "bind" the IP address to the MAC address of your router and that it changed for some reason between the stock firmware and OpenWRT. It may time out for you after a while, or, at worst, you may have to call them and tell them you have a new router. It should be straightforward for them to do, but I know what the wait queues for someone competent in technical support are like!
If you have a label on the bottom of the router, it typically gives the MAC address, something like 11:22:33:aa:bb:cc -- might be worth checking that against the MAC address shown in LuCI for WAN on the Network > Interfaces page. (Or, if you're running stock firmware right now, noting what it says in the stock UI.)
That actually worked! Thank you very much!
Great. What also often seems to work is power cycling both the docsis-modem and the router, as the MAC to DHCP address binding has a permissive initial phase and only after a short while it is fixed.
Thank you so much for the help