Tethering and Routing

As you may recall from an earlier post, I discovered my broadband connection at home was horrendously slow compared to my 4G/LTE connection on my phone. Now, I regularly tether my laptop to my phone and enjoy download speeds in excess of 1.2Mbps, compared to 300-400kbps over my home broadband. However, if you try to turn the phone into a WiFi hotspot, then my MNO (Three) doesn’t like it and asks me to pay £5 for a 2GB allowance. However, there doesn’t appear to be a restriction on physical tethering (and I’ve downloaded more than 2GB).

So, the question is, is it possible to tether my phone to my laptop and share that connection to other machines on the network? I suspect so, but it will involve me tinkering with my internet settings, and disabling settings in my broadband router, so it behaves more like a hub than a router.

My thoughts are (and this is subject to my tinkering):

  1. Configure my broadband router to not issue IP addresses — not necessary if you have static IPs on your network.
  2. Configure my laptop (which has the phone tethered) with a DHCP server so that it does issue IP addresses. Again not necessary if you have static IP addresses everywhere.
  3. If you have static IP addresses everwhere, change the default gateway to be the IP address to be the machine with the tethered phone (laptop in my case)
  4. Configure my laptop to route out packets via the gateway — notably, to switch on IP forwarding. From brief researching, this might require kernel recompiling, or at the least, module inserting via insmod or modprobe
  5. Make adjustments to the firewall (ipchains) to allow IP masquerading/NATting, preferably utilising security lock down, so not anyone can access the net via my phone.

If I can tear myself away from my newly found Final Fantasy XIV questing, I may try messing with my settings and see if I can get this to work.

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