IP Range for where you are.

Synopsis....

I needed to enable a range of IP's for use in an AWS Security Group so that other developers could access a test website I was working on. Here's how I found the smallest range, rather than opening it the whole world. NOTE: There is a small security issue with this method, it is described below.

All IP's pointing to me have been obfuscated...your eyes aren't going bad. :)

Step 1 - Find your IP

There's lots of ways to do this, but the quick simple way I use is simply going to

https://myip.ms/

And there's your IP!

Step 2 - Find Your IP Range

Now you know your IP. Now click on the WHOIS? icon and it takes you to the next page which shows you everything known about that IP. Who owns it, the IP range that is owned by them, etc.

Here's my general IP range:
X.X.128.0 - X.X.255.255    (32,768 ip)

So I want to figure out the short form of that IP Range.

Scroll down (or search) for CIDR. This is the value you want to use. The whole thing. For example, X.X.128.0/17 (it may be different based on the IP Range from above).



This CIDR is the value I used in the AWS console to denote my range of IP's.

Now the security hole here is that anyone in this set of 32,768 IP's can access my special website (on a specific port) that I setup with this particular rule. I'm ok with this small, if not virtually non-existent hole for my TEST website. Risk vs. Reward. I'll be sure to lock down the production site though.

More information on CIDR and what it means:
https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing