How Does Google Know Site IP?

[raveon]

I currently have several sites sharing the same IP. I'm breaking on out so that it will have it's own IP but with the same hosting company.

In an email to me this statement was made;

"Note that when changing from the shared IP to dedicated IP, HELM will leave the shared IP host headers in place."

This concerns me. Does Google even know what IP is in the host header? How does it determine your IP? Host headers or whois or Ping or what?

These sites reside on a Windows server.

[encyclo]

Googlebot gets the IP address from the DNS lookup like any other user agent. I think your fears are largely unfounded - you need the site to answer on both IP addresses during any DNS propagation period, Googlebot caches DNS lookups so it may continue looking for your site at the old IP address for a short while after the switchover, and serving one site from multiple IP addresses is never a problem as many larger sites do load-balancing for requests (just look at how many IP addresses there are for google.com) - it is never duplicate content as the URL remains the same for each request.