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Working around lack of router settings (lemm.ee)

submitted 8 months ago by [email protected] to c/[email protected]

31 comments fedilink hide all child comments

I am currently living with my parents and we have just started an Internet contract with a 5G wireless company.

The issue is the MFND settings are behind a password and likely not allowed access by the ISP. Even if they weren't doing port forwarding on 5G likely isn't possible because of CGNAT. I think I can use cloudflare tunnels or tailscale to get around this, and not many things need to be directly accessible from the Internet.

The more annoying thing is that setting DHCP reservations likely isn't possible without getting access to the settings. It's going to make setting up static IPs difficult too.

Before anyone asks fixed line Internet almost certainly isn't practical in this area. Getting our own modem while possible is more expensive and potentially difficult, and would mean cancelling the contract.

Is there a reasonable way to work around these issues?

Any help or advice would be appreciated.

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[–] [email protected] 13 points 8 months ago (2 children)

I use my own router with DD-WRT in-between the ISPs router/modem and my LAN, and use a different subnet. I haven't had any issues with this myself, and my router just sees the ISP router/modem as the WAN.

[–] [email protected] 5 points 8 months ago

Normally this is bad advice, but if you already have CGNAT you'd be going from double NAT to triple NAT and it probably won't make anything worse. At least it shouldn't make things worse for IPv4. If you have 5G internet with CGNAT there's no excuse for your ISP not giving you proper IPv6. Putting a second router between will complicate your IPv6 setup.

There are some tricks you can do for IPv4 in the precense of hostile DHCP servers. Serious OSes should allow you to configure a second IP address on the same physical interface, so you could have a dynamic 192.168.0.x assigned by the ISP's DHCP server and a static 192.168.1.y assigned statically by you, and then you should be able to set up an additional route table entry to access 192.168.1.0/24 using the source address 192.168.1.y. As long as the ethernet/wifi switching between devices doesn't filter ARP packets based on IP subnet, you should be able to communicate between your machines using fixed IPs on the second subnet.

[–] [email protected] 2 points 8 months ago (3 children)

Triple NAT? Would that cause any problems?

[–] [email protected] 4 points 8 months ago

Unlikely. The main issue comes with port forwarding, but you are locked out from doing that already. I say go for the triple NAT, put your own router after the ISP's modem and then you have full control of your LAN.

[–] [email protected] 2 points 8 months ago

Not really for most applications

[–] [email protected] 2 points 8 months ago

Yes, but probably no additional problems if you’re already behind CGNAT.