For a while, I had a problem with Googlebot being unable to crawl my site (and in fact I was having this problem for so long that my site was actually de-listed from Google).
Testing my site in Google Webmaster Tools with Fetch As Googlebot actually returned a blank page: Googlebot was unable to reach my site, and could provide no diagnostic message that could explain the lack of reachability.
What’s up with that?
As it turns out, for reasons still unknown, my correctly-configured networking service on my web server was bringing up its IP address with a
/8
netmask, instead of the (in my case) correct netmask of/24
.Manually removing the offending entry from my server’s routing table and adding the correct entry resolved the issue, and Googlebot is now happily visiting my web server again:
(IP addresses changed to protect the innocent. Adding the correct entry before removing the incorrect one helps keep your SSH session open if you’re connected via that address.)