Google has published a complete list of IP addresses used by Googlebot user agents. This is reported on the page on the latest changes to the search documentation.
A link to this list has been added to the help article: “How to make sure your site is crawled by Googlebot or other Google crawlers“.
Site owners can now identify Google crawlers by IP addresses, says SearchEngines.
NIX Solutions notes that verification is recommended, if there is a suspicion that spammers or other attackers are trying to access a site disguised as a Googlebot.
That being said, the previous version of the document also stated that Google does not publish publicly available lists of allowed IP addresses for site owners.
“Address ranges can change, and this would cause problems on sites if such IP addresses are specified in their code. Therefore, for verification, you need to perform DNS queries, as described below. “
This note no longer appears in the updated document.