(Very Basic) TCP/IP Troubleshooting in Windows
Then you might need to do some basic TCPIP troubleshooting. I recommend at least trying the stuff I'm talking about here before you call your ISP technical support line.
Then, when you talk to your ISP's tech support people, you can give them some useful information that will help them identify your problem a little quicker than the stock "Let's reboot your system/cable modem/DSL box etc. and see if it works then" answer.
To be fair to the overworked and underpaid level-one tech support people out there, sometimes a simple reboot does clear up a problem. So save yourself a wait on hold
At worst, the poor new techie on the other end might say "huh?" If so, you can point their supervisor here for some tips about how to train their support staff to do their jobs a little better <evil grin>.
Most of the tools I'll tell you about here run from the Windows command line, AKA an MS Dos Session. In case you don't know how to open a command line session, here's the easiest way:
In Windows 9x or ME, do this:
In Windows NT, 2000 or XP:
A short rant about Windows:
Useful command line tools
In Windows, you can open a command line session, and type (for example) tracert www.yahoo.com. You'll see something like this:
Each numbered line represents one "hop" along the route between you and Yahoo. It shows you three time values, the "friendly name" of the router you crossed, and the numeric IP address of the router you crossed.
Tracert sends three packets out, and the three numbers indicate the time in milliseconds that it took those three packets to travel from you to that router.
If you see three * results within the first two or three "hops," the problem is very likely with your Internet Service Provider's networking equipment. Knowing this, it can be worthwhile to phone them, and ask nicely if they are aware of the problem, and how long it might take before things work again.
Note that many corporate network firewalls don't pass tracert packets for security reasons. My workplace's network is one such environment.
If you didn't make a typo in the address part of the command, you may need to fall back on more basic network/Internet diagnostic tools.
Windows 9x and ME all have a graphical diagnostic tool that lets you see your TCP/IP network settings. It also lets you do useful things such as releasing and renewing your "automatic" network configuration (DHCP, or Dynamic Host Configuration Protocol) settings.
If your system is set up to get "automatic" settings from a DHCP server, you may need this tool. Even the Windows XP networking layer can get "confused" and not be able to connect out.
There's no icon for it in the Start menu, so you have to get at it this way:
To see everything you might need to know about your IP settings, you might have to click the More Info button, or or choose a different network interface in the pull-down list at the top.
If you're trouble-shooting a running dialup connection, you to look want the PPP Adapter. If you're on a cable modem or other broadband connection, choose that network device from the list.
This information is pretty hairy network geek stuff, but if you have even one bad setting here, guess what? You can't get or send email, see web sites, or do much of anything else on the Internet. The lights are on, but nobody thinks you're home.
If you like mucking about at the command line, the good news is that all the 9x versions of Windows (including ME) also give you <ta-da>:
If you run Windows NT, 2000, or XP, guess what you don't get? That's right; you don't get the somewhat friendlier winipcfg graphical diagnostic tool. And brave Win9x-ers can do this too!
Some of you on Windows 9x, or NT might have had some of that wonderful "help" content scroll off the top of your screen. You may need to type "ipconfig /? | more" to see all of it.
My two favourite ipconfig commands
Solving Automatic Configuration Problems
Every version of Windows -- including XP, can sometimes go "stupid" at the network layer. But instead of rebooting, try either Winipcfg or ipconfig to first "release" and then "renew" your network settings.
If you get an ugly error message on the "renew," read it and/or print it out. You will want to refer to it when you call your ISP to report the trouble.
Expect them to say something like "OK, reboot (your system, the modem, or the whatever)." You'll say back to them, "Yes, I've been there, done that, didn't get a t-shirt, and now when I run ipconfig (or winipcfg) I get this (read it to them) error message."
"Ping" was named after the submarine sonar echo-location technology. You "ping" a resource, and if you don't get a response, it's not there for you right now.
If you type "ping /?" you'll get another one of those friendly dos command line help screens with all the syntax you can add on to refine the basic ping command. The useful thing is, you can "ping" either a numeric address or a named address.
Either way, you'll get back something like this:
Pinging 192.168.1.1 with 32 bytes of data:
The time= statement shows you the response time from the remote machine. Machines close to you will answer with faster times than machines far away, unless there are problems with congestion on the route to the machine.
In that case, you can run a tracert to see where the congestion is.
When to use ping
When diagnosing internet connectivity, ping can tell you some very basic information.
Check your winpcfg or ipconfig to see what the numeric address of your gateway is. Then type ping 192.168.1.1 or whatever the numeric address of the gateway is.
If the gateway answers your ping, it's probably running OK. And you know that your machine is OK too, because it can talk to the gateway.
Next, ping the numeric IP address of your primary and secondary DNS servers. If they answer, probably (but, again, not always) they are running OK.
Next, ping a named address, something you know is likely to be running OK, like www.yahoo.com, or www.ibm.com, etc.
If you get ping responses from the numeric addresses of your gateway and DNS servers, but not an outside named resource, something is definitely wrong somewhere. "Unknown host www.yahoo.com" is not a helpful error message, but it can be.
Maybe you made a typo in the address. Or maybe your primary and secondary DNS servers both "went stupid." That happens too.
If you get "unknown host" errors, it means you have a DNS problem (your settings are wrong, or the DNS servers are down, or the routing is gone, or…)
"Request timed out" is only slightly more useful. The DNS boxes are running and recognize the name, but you still can't talk to it.
That's when you reach for our old friend tracert to see where the problem is.
If you work on a corporate network with a locked down firewall, you probably will not be able to use ping (or tracert) to diagnose connectivity to resources outside the firewall. Many corporate firewalls lock out the ICMP protocol and the TCPIP ports that the ping and tracert commands use.
I can predict one of the first things that will happen after you call your corporate help desk to report a network problem. They will "ping" your workstation to see if its network layer is running.