Attention all readers: Sorry for the fomatting mess below. At some point the site changed how it handles HTML in FAQs and this is the result. I'll try to get it cleaned up as time permits. -RadioDoc

Given the state of some "technical support" departments at some of the major DSL mass-market providers; it is sometimes useful to identify an ISP related problem specifically. "My e-mail is down" you tell tech support. "Well, no one else is having that problem" or "everything looks good at this end; let's format your drive!"

Sometimes it's a good idea to call tech support with a specific technical report. It helps to cut through much of the BS.

So, you are surfing along, and suddenly your browser complains that it can't find yahoo! Before you call your trusty ISP, poke around to see why the browser can't find yahoo.

You first bring up a dos window. Enter "ping www.yahoo.com" What you get back is "Unknown host www.yahoo.com." So, my computer can't turn a name into an IP address... DNS (Domain Name System) issue. Call tech support now? Nope, not yet! Let's see WHY yahoo is UNKNOWN first.

You search through those papers your ISP sent when you got the account, along with your setup notes and find that your DNS server is 123.123.123.123. OK let's see if it is working!

You bring up a DOS prompt. Type "ping 123.123.123.123" and you get:

Reply from 123.123.123.123: bytes=32 time=110ms TTL=53

Reply from 123.123.123.123: bytes=32 time=110ms TTL=53


OK, so it "seems " to be up, but is it really up?

Let's look into it further. We will use windows telnet to look into this problem. Why telnet? Well, it exists on all windows boxes, and is free.

1) Using windows telnet: [CONNECT -- Remote System]

2) Under "Host Name" enter the IP ADDRESS of the target DNS Server, 123.123.123.123

3) Under "Port" enter the NUMBER "53" instead of the default "Telnet".

4) Click on "Connect"

Now, several things can happen depending on the status of the target DNS server.

What we are doing here is simulating what your client software (the browser in this case) is doing when it needs to resolve a name like yahoo.com into an IP address..

If you have a good dns connection at this point, the cursor will go home (the upper left hand corner of the telnet screen). You will not be able to type on the screen, but a "CONNECT -- DISCONNECT" will work, and disconnect you cleanly.

This means the target system responded to a DNS request on its DNS port 53. This can mean that something is wrong with your networking setup. Possibly the DNS servers have changed IP address, or your networking properties defining DNS server IP addresses have changed. It is not impossible, but improbable, that it could be your ISP's DNS server, or connectivity related issue.

If you have a bad dns connect, after you click on the connect button, either you will see a perpetual hourglass which has to be killed by task manager; OR the error "Connect failed could not open a connection to 123.123.123.123" will appear on your screen. This means that your ISP's DNS server is not servicing port 53. This indicates that the DNS server is down. Even though it can be pinged, it is not servicing DNS requests.

Armed with this information, you now call tech support, and report that their DNS server is down. You know this because it has a dead port 53! When will it be fixed? By the way, do you have an alternate DNS server I can use??

This same troubleshooting technique can be used to test other ISP related services. Most Internet services which your ISP provides can be tested this way.

Try using this technique on your ISP's Mail server, use the number 25 for the SMTP port (instead of 53 which is for the DNS port), see if they are up, see what it looks like when they are up so you will know the difference when it is down. Try their port 110 POP3.... 143 IMAP etc...

Check out your primary ISP server-provided services this way the next time you have a problem, or suspect that your service provider is not providing a particular service.

Then call them, and report your findings specifically. You will get better mileage from your broadband connection and better "service" from tech support if you do some of the homework yourself.

This FAQ entry written and submitted by bobrichards

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by RadioDoc
last modified: 2008-10-07 13:45:21