I used Apache’s mod_rewrite in order to direct a couple of domains pointing to the same website using the 301 moved permanently (to avoid duplicate content), i.e. something like this in .htaccess:
RewriteEngine On
RewriteCond %{HTTP_HOST} !^example\.com$
RewriteRule ^(.*)$ http://example.com/$1 [R=301,L]
I randomly got the error message 310 ERR_TOO_MANY_REDIRECTS when trying the different domains in both Chrome and Firefox (other browsers seemd to work). I had decided my site should be reached without "www", so http://www.example.com was redirected to http://example.com also.
After a while of head scratching I found a couple of forgotten DNS entries. Two of them where outdated. My domain setup for example.com in DNS looked like this (sample IP-addresses):
example.com zone:
@ IN A 192.168.100.1
@ IN A 192.168.100.2
@ IN A 192.168.100.3
www IN A 192.168.100.1
But only 192.168.100.1 was valid and had a running web server on it.
I guess what happens is when Chrome/Firefox tries to talk to 192.168.100.2 or .3 and get no response, they add "www" in front of the domain name, i.e. http://www.example.com. Now it got a response from the webserver saying 301 redirect to http://example.com. Now trying to talk to example.com on 192.168.100.2 or .3 no response, adding "www" and there we have our loop.
Fixing the DNS entries (removed the invalid 192.168.100.2 and .3) fixed the problem. A bit odd and hard to find, and most of all stupid to have the outdated records still in the zone.
