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onlysublime
Gerbil
Topic Author
Posts: 87
Joined: Sat Jul 16, 2005 3:20 pm

DNS puzzle. can't access 1 website

Tue Mar 09, 2021 9:16 pm

I've been wracking my brain over this problem. I have no idea what to do anymore.

So, my friend told me she couldn't go to stamps.com on her computer at work. I try it on my computer and I can't access that website either. However, we can access pretty much all other websites. So then I try the basic clear all caches, cookies, browsing history, etc. Still no go. I rebooted the computer (Windows 10 20H1). Still no good. I turned off the firewall. Still no good.

I then asked a friend in a different office in the building to try and he can't access the website either. They have their own Internet through the same ISP. So I think it's the website that's the problem.
But Stamps.com shows all fully operational on their status page. I then think it's the ISP problem. I

I then tried flushing the DNS. Still no go. I tried setting the DNS to Google's 8.8.8.8 and 8.8.4.4 and still no good.

I try both Edge (Chromium browser) and Internet Explorer. Still no go. Then I tried Mozilla Firefox and it works. So I thought, aha! It's a browser issue. HOWEVER, I then go to my phone and I can't access the website when connected to our WiFi or my friend's WiFi. However, if I disconnect the WiFi and connect via my mobile network, I can connect! Using the same browser!

It's driving me crazy. I don't know what to think. This site used to work on every browser we tried. The problem just started this afternoon. We also use Stamps.com through their software. However, the software cannot connect. We know their software uses Internet Explorer as their backbone.
 
Wirko
Gerbil Team Leader
Posts: 296
Joined: Fri Jun 15, 2007 4:38 am
Location: Central Europe

Re: DNS puzzle. can't access 1 website

Wed Mar 10, 2021 4:38 pm

First try all variants in your browsers: http://stamps.com, http://www.stamps.com, https://stamps.com and https://www.stamps.com . The first three should be redirected to the last one.

Try to determine the IP addresses of the web site in command line:

nslookup www.stamps.com
Address:  45.60.155.44


nslookup stamps.com
Addresses:  45.60.171.44
          45.60.151.44


If you get a "Non-existent domain" message then it's a DNS-related error. If the IPs you see are different from those above, your OS still has old DNS records in its cache (somehow).

You have the curl tool available in Windows 10 command line. Try to get some response from the web server:

curl --header 'Host:www.stamps.com' http://45.60.155.44

curl --header 'Host:stamps.com' http://45.60.171.44

curl --header 'Host:stamps.com' http://45.60.151.44

A giant chunk of HTML code is supposed to be printed out after each command. If you get an error message, it means that the access path from you to the web server is blocked by some firewall.

I used the same command in the 'online curl' tool at https://reqbin.com/curl since my Windows is No. 7, the one without curl.

Also, some DNS history is available at:
https://securitytrails.com/domain/www.stamps.com/history/a - the IP for www. stamps.com hasn't changed in more than a year
https://securitytrails.com/domain/stamps.com/history/a - new IPs for stamps.com since March 1st, 2021. This could be the root cause of your problem, maybe the IPs haven't propagated to every DNS server and DNS cache yet.

Oh, and thanks for stopping at TR and asking for help. I've learned some new useful things when putting all this together.
 
onlysublime
Gerbil
Topic Author
Posts: 87
Joined: Sat Jul 16, 2005 3:20 pm

Re: DNS puzzle. can't access 1 website

Thu Mar 11, 2021 2:11 am

thanks for all the help. really appreciate it and I'll keep your techniques in mind when stuff like this happens. In fact, I'm bookmarking this thread so I can refer to it. I'm not particularly well-versed in networking so stuff like this helps me learn.

So about 2 hours after I posted this thread, everything started working again even though I didn't do anything. Does that mean the IPs finally propagated to all the DNS servers?

And thanks again. :)
 
Wirko
Gerbil Team Leader
Posts: 296
Joined: Fri Jun 15, 2007 4:38 am
Location: Central Europe

Re: DNS puzzle. can't access 1 website

Sat Mar 13, 2021 10:19 am

Yes, obviously. I can't explain where those old DNS records were stuck for so many days, and why.

I suggested using curl, however, you can also use a Firefox extension called LiveHosts for the same purpose. It lets you access a website with a domain name you type in and IP address you type in, ignoring any DNS cache and DNS servers, if you suspect that they hold invalid or old data.

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