Essentially I'm answering my own question here, but want to provide this info to anyone else who might need it. I need all the valid IP address ranges for Google Apps mail servers.

I'm configuring a firewall to only allow incoming SMTP from our Google Apps hosted (POSTINI) email and want to allow only the expected servers to connect to our internal server for delivery. In trying to setup the rules in our firewall, it does not accept CIDR notation for the allowed IP address ranges. Thus I have had to convert them from the CIDR addresses provided by the article: Google IP address ranges

NOTE: This is not a duplicate question. The article linked to as a duplicate reference is "how does IPv4 subnetting work". This is not what this question/answer asks or answers. This article is to save others the time to do each of those conversions manually from Google's published list of addresses if they have network equipment that doesn't accept CIDR notation.

  • 1
    I appreciate that you are trying to help others out here. The problem with this QA is that its usefulness is very time-limited. Assuming your list was 100% accurate when you posted it, it's only going to become more and more inaccurate as time goes on and as they add/remove netblocks. Your link to the Google Support page is great - people can consume that information and then use knowledge gained on the duplicate linked page to know how to convert from CIDR to a mask.
    – EEAA
    May 11, 2015 at 19:15
  • This should be re-opened. There are automated ways to find out this information, including through SPF.
    – cnst
    Jul 3, 2016 at 17:46

2 Answers 2

CIDR              Subnet Mask       Starting IP     Ending IP

I have this one too-

IP : | Subnet :

Range : -

here is a link to a calculator: http://www.subnet-calculator.com/cidr.php

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