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If I go to my website it loads fine. I can use my VPN to jump to various different countries and it also loads fine.

However, one potential client cannot see it. Not only that but the site http://isitdownorjust.me also shows it as being down.

Pingdom.com shows the site as being up across all of its different ping centres.

Can you help explain what might be causing this? I assume it's a DNS issue but I don't know where to start to solve it.

  • 2
    When is the last time you updated your DNS records? Recent updates can take a while to propagate. – Stephen Ostermiller Feb 23 '17 at 18:25
  • Months and months ago - wouldn't be that – Peter Nixey Feb 24 '17 at 10:15
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This can be caused by DNS. If your DNS records return different results to different people, you could have a problem.

There are two ways that could happen:

  1. You have multiple A records with different values

  2. You have to have multiple DNS servers that have different information.

Here is how to check using the command line program dig:

  1. Look up the name servers using dig NS:

    $ dig NS copyin.com
    ;; ANSWER SECTION:
    copyin.com.     86225   IN  NS  anuj.ns.cloudflare.com.
    copyin.com.     86225   IN  NS  daisy.ns.cloudflare.com.
    
  2. Look up the records on each of the nameservers using dig @

    $ dig @anuj.ns.cloudflare.com copyin.com
    ;; ANSWER SECTION:
    copyin.com.     300 IN  A   104.24.124.141
    copyin.com.     300 IN  A   104.24.125.141
    
    $ dig @daisy.ns.cloudflare.com copyin.com
    ;; ANSWER SECTION:
    copyin.com.     300 IN  A   104.24.124.141
    copyin.com.     300 IN  A   104.24.125.141
    

Your two nameservers appear to have consistent information, however they each have two A records with different IP addresses. This implementation is called "round robin DNS" and it will cause clients to randomly get one IP address or the other.

It could be that this is on purpose and those two IP addresses are both available to serve your site. It could be that only one is correct and users that get the other get errors. It could be that they are both correct, but sometimes one or the other goes down.

When users are having problems you can test it two ways:

  1. Edit your /etc/hosts or hosts.txt file to manually point your local machine to a specific IP address. Then visit the site in your browser.

    104.24.124.141 copyin.com
    
  2. Use the command line program curl like this:

    $ curl -H Host:copyin.com --head 'http://104.24.124.141/'
    HTTP/1.1 301 Moved Permanently
    Location: https://copyin.com/
    
    $ curl -H Host:copyin.com --head 'http://104.24.125.141/'
    HTTP/1.1 301 Moved Permanently
    Location: https://copyin.com/
    
    $ curl -s --resolve copyin.com:443:104.24.124.141  'https://copyin.com/' | grep -i title
    <title ng-bind='PageMeta.title'></title>
    <meta content='Copyin' name='apple-mobile-web-app-title'>
    <page-meta title='Copyin - Next Generation Email Groups'></page-meta>
    
    $ curl -s --resolve copyin.com:443:104.24.125.141  'https://copyin.com/' | grep -i title
    <title ng-bind='PageMeta.title'></title>
    <meta content='Copyin' name='apple-mobile-web-app-title'>
    <page-meta title='Copyin - Next Generation Email Groups'></page-meta>
    

It does appear to me that both servers are up and running with your site right now. You should try the same thing when somebody reports having problems.

Since you are using Cloudflare, it could also be somewhat more complicated than this. Cloudflare is a content delivery network (CDN) that uses DNS tricks to try to route users to their "edge network". That is they host servers all around the globe and the DNS somehow points to different places for different users. I'm really not sure how to debug all the possibilities that Cloudflare might put in DNS. My only suggestion would be to ask them to open a command line and ping your site. Ask them for the IP address and test against that yourself.

  • Super helpful answer, thank you Stephen. I'll start by checking those A-records and will then report back on how it worked and mark the question right if so. – Peter Nixey Feb 24 '17 at 14:50
1

Are they trying to access your page from a School or Corporate network? IT might be due to a filtering policy enforced on their network. There also could be other issues inhibiting them from seeing your page. such as Ad blockers and so forth.

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