Accessing Arris S33 Modem Behind Router

Installing and Using OpenWrt Network and Wireless Configuration
1

I have an Arris S33 Modem which works well. It only has one annoying quirk which it that it blocks access to the Admin page for all machines behind a router. If I plug a computer into the modem directly and go to 192.169.100.1 I can access the modem's admin page fine.

However once I put same computer behind the router, nothing. My old Netgear Modem has no issue with this, it is a known limitation of the Arris S33.

I can get it to work if I take a custom Wifi SSID such as "Modem Admin", bridge it to the wan, connect a computer to it, and then give it a manual IP of 192.168.100.5. But I don't want to have to do all of that.

I've got a pretty complex setup and understand networking decently well, but I cannot figure out how to expose this address to the rest of my network transparently to the modem so any machine can just hit 192.168.100.1 and get to the admin page.

Any ideas?

https://openwrt.org/docs/guide-user/network/wan/access.modem.through.nat Tried this and it prevents me from accessing the internet. Turning the interface on kills internet access, turning it off restores it. I suspect the modem responds back on the wrong Interface.

2

Configuring an alias interface as described there should work - and it did, while I was still on VDSL with a modem interface.

3

Creating the alias makes it such that I can no longer access the internet. The second I enable the interface, my internet connectivity goes down. :-/

4

Well, crystal balls are in rather short demand these days, so guessing what you ended up with is a tad difficult (hint, paste the changed configuration).