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Setting up NTL:home broadband
The cable TV company NTL provides a broadband internet service through TV cables. This article explains how to configure a Linux box to access this service.
Linux Support
NTL:home does not support Linux or Intranets. They will not penalise you if you are running Linux or connecting up an Intranet, but they won't be able to give you technical support. In fact, NTL:home's technical support seems to be limited to saying "switch off the set top box at the wall, wait half a minute, switch it back on again, and if it still doesn't work try re-installing Windows."
Preliminaries
The NTL:home receiver has an RJ45 port on the back panel which can be connected to a standard network card. IP addresses are allocated by DHCP, but the lease seems to be fairly long-term (in the author's experience, only one change in nearly two years' use, and this was due to a power failure; my configuration is set to renew the lease every 3 hours. Dynamic DNS should work. I have actually pointed a (static? Crazyeddie) domain at my address. I would not recommend specifying an NTL allocated address as a mail exchanger, though; stick to fetchmail.) Dynamic DNS should work though.
Brokennesses with NTL:home
The service is tied to the MAC address of the ethernet card plugged into the set top box. NTL:home web space does not have any kind of scripting support. NTL:home does not provide virtually-hosted e-mail. This means you will need to get an account with a real ISP if you want to do more than look at other people's web sites and delete spam from your inbox. I recommend [UKLinux] -- you get true virtual hosting, perl and PHP, MySQL or postgreSQL, procmail, SpamAssassin, an Envelope-To: header, and their fees are very reasonable. You can still use the broken NTL:home web space to store photos, soundbites or something that can be downloaded verbatim.
DHCP
There are several DHCP clients available, and your distribution may already include one. In the author's experience, pump does not work for anything past the initial provisioning stage; dhcpcd works fine.
Configure your chosen DHCP client, cross your fingers and plug your network cable into your set top box. If all goes well, when you type /ifconfig you should see that you have a 10.x.x.x IP address bound to the network card.
Provisioning
When you first connect to the network, you need to go to a provisioning server to register yourself using the details in your welcome letter (the Windows installation CD does this for you). You will have to call the helpline to obtain the IP addresses of the provisioning servers, which will be unroutable addresses starting with 10; and (unless you have a working BIND) the nameservers, which will be real, routable addresses. It's a bit of an unusual request, and you'll probably be kept waiting to speak to some arch-wizard; just stay calm and try not to think about the fact that you are paying these people's wages (after all, they clearly don't).
Once you have an address for a provisioning server (try 80.5.178.26), connect to it using a web browser and fill in the form. A text-based browser should work fine for this.
After Provisioning
If you were using Windows, you would have to restart your computer about now, because the far-end DHCP server has a new IP address for you. (Or you could enter ipconfig /renew_all in the command line. Exact syntax varies between Windows versions, use ipconfig ? or --help to check.) But all you probably need to do is send a SIGHUP to your DHCP client, in order to make it check for a new IP address; and edit /etc/resolv.conf to install the nameserver addresses. You should now be good to go, with a routable IP address, and you should be able to ping boxes.
Sharing a Connection
It is possible to share a connection. You will need two ethernet cards, one for the Internet (broadband) and one for the Intranet (LAN). Just set it up as you would any NAT firewall/router.
Of course, to share your NTL-home connection you could also just dive straight in and buy a DSL gateway/router instead of another network card. These are fairly cheap nowadays and the benefits of this include:
- Firewall on the router itself protects all computers on your local network at same time.
- NAT by the router so outside world can't even see your local computers.
- All machines on your home network are independent - you can turn any off without affecting the connection at all (so you wouldn't always have to leave your routing PC on when using your internet connection from another machine).
- One machine isn't slowed down due to acting as a router for another.
- You can normally connect more than just one other machine (say, wife's laptop as well as the kid's games machine, plus your Linux box of course).
- You've got the possibility of WiFi support on the router too (if you pay a bit more).
I opted for the DSL gateway/router setup for my NTL-home connection and it works fine.
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