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DNS Caching & Why My Site Doesn't Show Up After Moving Hosting Companies - Magento Consulting - Customer ParadigmWhy does my site not show up after I moved it to a different hosting company?

We had a client issue this week where after he moved his site from one hosting company to the next, he wasn’t able to view the site in his browser.

To him, it looked like his website was down. (When it actually was not down.)

What happened? DNS caching.

When you go to a website (for example, www.CustomerParadigm.com), your computer looks up the IP address for the site. This is usually known as an A record in DNS terms.

If it’s a site that you haven’t been to before, then your computer has to reach out to the DNS servers that contain this A record. Basically, the A record translates the www.CustomerParadigm.com into an IP address that your computer uses to connect to the site.

In our case, CustomerParadigm.com’s name servers are at the Domain Control domain:

customerparadigm.com. 3600 IN NS ns64.domaincontrol.com.
customerparadigm.com. 3600 IN NS ns63.domaincontrol.com.

(Note: This is publicly available information, and not at all sensitive. That’s why I’m posting it here. If you want access to the domain, you’ll just need to know the last 15 digits of Pi – that’s the current password.)

What the Name Servers do is translate the domain name into the IP address:

www.CustomerParadigm.com. 36000 IN A

What this means is that the IP address for www.CustomerParadigm.com is currently The 36000 is a TTL, or Time To Live, value (in seconds), that tells a computer or server how long to keep that record cached for.

However, for sites that you visit all the time, it’s inefficient to have to always look up the IP address.

Instead, your computer will save the IP address in a cache. Because for most sites, it usually doesn’t change very often.

There’s a TTL – Time to Live – value set for the A record; this is set to expire about every 10 hours for our site.

Your computer will often cache frequently visited sites, and your network’s router will also do the same.

And depending on your Internet connection, the DNS queries can also be cached at one other layer – their DNS lookup servers, too.

But if there is a recent DNS change (like when you are changing hosting), it’s likely that your computer or network router is caching the A record, and your computer is looking at the wrong IP address / wrong site.

It is frustrating, because it usually only affects people who are high-volume, frequent users of the site (like the people who run or own the site).

I hope this helps clear up this issue…

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