Help me understand my basic home internet setup.

December 12, 2010 10:34 PM

I wish I could troubleshoot my home internet service and wireless network when they're acting funny. I'm computer-literate but I only have the vaguest sense of how networks do what they do, I don't mind reading technical stuff, and I'd like to end up with a useful set of intuitions about how the damn thing works. What should I read?
posted by nebulawindphone to computers & internet (11 answers total)

the man pages for ping and traceroute couldn't hurt.
posted by trondant at 11:23 PM on December 12, 2010

The Wikipedia pages for ping and traceroute explain them in something more like essay form. The pages for Internet Protocol and packet are probably helpful too. But I don't disagree that the man pages are a reasonable place to start.
posted by Monsieur Caution at 12:23 AM on December 13, 2010

http://en.wikipedia.org/wiki/TCP/IP
This covers the basic technology underlying most modern Internet-connected networks

http://en.wikipedia.org/wiki/Home_networking
As applied specifically to home networking

http://en.wikipedia.org/wiki/Domain_Name_System
Something you might occasionally need to understand as it's a pretty weak point in the whole system. Since I've had Comcast, 9 out of 10 times I have a connectivity problem it's this.
posted by thesmophoron at 12:33 AM on December 13, 2010

So I appreciate the tips, but this is precisely the problem I'm having. There's a lot of basic domain knowledge that's presupposed by those man pages — and if it's there in the corresponding Wikipedia pages, then I don't even know enough to recognize it when I see it.

For instance: Okay, I gather ping tells me whether I'm "in touch with" a particular IP address. But how do I use that information? Which addresses should I try pinging, and why? The man page says hosts and gateways further and further away should be "pinged". So let's say I get a reply from one "nearby" address and not from another "far-off" one — what do I do now? How do I translate that into a practical step like "change such-and-such a router setting" or "call up my ISP and bitch about such-and-such"?

I feel like the answers to these questions should be obvious, if only I knew what J. Random Manpage Reader knows about networks. Is there a good introductory book or something that will get me to that basic level of knowledge?
posted by nebulawindphone at 5:38 AM on December 13, 2010

"... I feel like the answers to these questions should be obvious, if only I knew what J. Random Manpage Reader knows about networks. ..."
osted by nebulawindphone at 8:38 AM on December 13

Unfortunately, a lot of TCP/IP network engineering is "recommended" or "best practice," not a requirement. For example, many ISP's deliberately configure some or all internal routers/switches in their networks not to respond to ping or traceroute requests on normal ICMP ports, to protect their network topology from being easily discoverable by customers. There's nothing wrong with this, as implementing compliance with ICMP message protocols for all network equipment is not mandated by anybody setting Internet standards; a lot of actual Internet operation lore like this you pickup, if you're so inclined, by study, or work in the network industry, or by subscribing to fairly geeky network management mailing lists or newsgroups for awhile.

But if you're looking for a single book to start your self-education, I'd recommend Internet Routing Architectures by Bassam Halabi as a good starter text. Published in 1997, it's a bit dated now, is pretty heavy on Border Gate Protocol routing setups (which are beyond the scope of most home users requirements, except as discussion cases for describing routing situations), and doesn't talk much about coming IPv6 protocols (relevant as we approach IPv4 address exhaustion), but it is still a good start to understanding basic routing and device concepts.
posted by paulsc at 6:30 AM on December 13, 2010

The O'Reilly TCP/IP Network Administration book is good. Some parts will be inaccessible at first but after reading it you will be well on your way.
posted by ChrisHartley at 7:32 AM on December 13, 2010

here's an example of how you'd use some of these network tools, what what the responses tell you. in this example, you can't seem to get to any webpages but you're connected to the wireless on your home network.

ping the router's ip address, if this works, the router is at least partially up.
ping your DNS servers, if they respond, at least you should be able to resolve host names into routable IP addresses.
nslookup or dig of a few websites to check that your DNS servers are resolving IP addresses correctly. the DNS server is responding with valided data.
run a traceroute to various sites. you see the traceroute go out your router, to your ISP, got to your ISP's up stream provider, but then seems to bounce back a forth without actually getting to your destination.

what you've learned? your network setup is fine, but somewhere past your ISP, there is a routing table misconfigured and the traffic can't get through upstream. you could call tech support and let them know, but they're probably already aware.

if you fail at an of the earlier steps, say, DNS, you could try moving your DNS servers to a free provider, like OpenDNS, instead of the ones provided by your ISP. this has been an issue of late for Comcast. If you can't even ping your DNS servers, this probably means the problem is with your modem. if you can't ping your router, the problem is with your router...
posted by jrishel at 7:48 AM on December 13, 2010

Will the Halabi book or the O'Reilly talk about wireless-specific issues too? Or should I look somewhere else for that?
posted by nebulawindphone at 8:36 AM on December 13, 2010

The Halabi and O'Reilly books probably don't cover wireless specific issues since those are separate from TCP/IP. Reading the books mentioned above will give you a deeper understanding of how things work. That will probably help you fix them when they don't work but if you are looking for just how to fix things there are better resources.

In my experience there aren't a lot of things that can go wrong with wireless. Either the security settings are misconfigured/not supported by the client hardware or a cordless phone, etc is causing 2.4Ghz interference
posted by ChrisHartley at 8:49 AM on December 13, 2010

tl:dr? turn everything related to your home network off/unplug it, wait 90 seconds, turn it back on/replug it. Fixes many plroblems.

Here's something you could try: lecture notes from a community college's Computer Networking class. Link

A run through the PowerPoint slides or notes might help fill you in.

There are two types of IP addresses, let's call them external and internal.
You get an internet connection through your service provider issuing an external IP address to your modem. If you can see the other computers on your home network but can't get to www.whatever.com, the problem is external, somewhere between the service provider and your modem. Call your service provider for assistance? Usually a 'remote reset' of your modem and waiting 10 minutes will do the trick.

An internal IP address, identified as usually starting with 192.168.x.x or 10.0.x.x, is something that your router (wired or wifi) creates and passes on to the devices in your home network. Metaphor: your ISP gives you one phone number, and your home router becomes a switchboard, issuing extension numbers to each device, enabling them to either talk to each other internally or dial an outside line to get on the internet. If you can't connect to anything at all, and/or don't have an IP address, then the problem is internal, between your computer and the router.

Assuming you're using the Windows command line (Start>Run>cmd), here's the quick and dirty:

type in ipconfig /all = that will display the current networking data for that computer
you can skip most of it except for:
IPv4 Address = the internal IP address of your computer
Default Gateway = the internal IP address of the device between you and the internet, probably your modem
DHCP Server = the IP address of the device that issues your computer an internal IP address (also probably your router)

ping the IP address of your DHCP server - do you get a response? Good, that means your computer and your router are communicating.
ping www.google.com - do you get a response? Good, that means you can contact the internet from your computer.
A no answer will help you do the process of elimination to figure out where the problem lies.

Go to your web browser and type in http://theIPaddress of your router (see DHCP server above, or look for a sticker on the router listing the default address, probably something like 192.168.1.1). That will get you to the configuration page for your home networking gear; you can find out a lot more there, and do things like permanently set IP addresses, so you always know which device is using which 'extension number'.
posted by bartleby at 3:05 PM on December 13, 2010

I wrote a little backgrounder a few months back that might be of use to you.
posted by flabdablet at 7:28 PM on February 27, 2011