It is useful to know Gmail’s IP ranges for whitelisting in your firewall.
dig _spf.google.com txtYou’ll notice that 3 results are returned _netblocks.google.com, _netblocks2.google.com and _netblocks3.google.com. You’ll need to query each of these in order to get the full IP range Gmail uses.
dig _netblocks.google.com txtdig _netblocks2.google.com txtdig _netblocks3.google.com txtThe first and third DIG results will return IPv4 address ranges, and the second DIG result will return IPv6 address ranges.