Your Blog, Custom Domains, And The Quadruplet Google Apps Servers

Some people can't see the forest, for the trees. Occasionally, we see a query from a perplexed blog owner, seeking to publish to a custom domain.

Google wants us to repeat the same IP address 4 times?

216.239.32.21
216.239.34.21
216.239.36.21
216.239.38.21

Uh, aren't they're the same? Why the needless duplication?

Like quadruplets (newly born human children), you may need name tags to distinguish one server from the other.

But, if you look closely enough, no, they aren't the same. As always, I'll present these examples using excerpted Dig logs.

mydomain.com. 3600 IN A 216.239.32.21
mydomain.com. 3600 IN A 216.239.34.21
mydomain.com. 3600 IN A 216.239.36.21
mydomain.com. 3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

"ghs.google.com" is a DNS server array, with multiple levels and multiple redundant parts. We use "ghs.google.com" to resolve the "www" alias of the domains, using "CNAME" referral. Most custom domains are published to the "www" alias - so "ghs.google.com" is massively robust, with redundant parts.

If we use a similar "CNAME" referral to resolve the domain root, aka the "naked domain", we could interfere with resolution of email, FTP, and other possible auxiliary domain services hosted, by the registrar. Instead, we use multiple "A" referrals, mutually redundant.

Long ago, until November 2008, we used "64.233.179.121", "66.249.81.121", and "72.14.207.121", which were triple mutually redundant equivalents of "ghs.google.com". And, you could easily see "64.233.179.121", "66.249.81.121", and "72.14.207.121" as different IP addresses.

mydomain.com. 3600 IN A 64.233.179.121
mydomain.com. 3600 IN A 66.249.81.121
mydomain.com. 3600 IN A 72.14.207.121
www.mydomain.com. 3600 IN CNAME ghs.google.com.

Now, we use the quadruple mutually redundant configuration. And, "216.239.32.21", "216.239.34.21", "216.239.36.21", and "216.239.38.21" are different IP addresses, though they look the same - if you don't look closely enough.

mydomain.com. 3600 IN A 216.239.32.21
mydomain.com. 3600 IN A 216.239.34.21
mydomain.com. 3600 IN A 216.239.36.21
mydomain.com. 3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

Theoretically, you only need one DNS server - for any domain. Realistically, though, not one server has an unlimited life span - and is 100% reliable.

If your registrar or hosting service does not support 4 x "A" DNS addresses setup, you may want to use a (free) third party DNS host. Now, here's hoping that your registrar allows easy configuration of third party DNS service.