Setting CIDR/IP so anyone can access it from any IP?

For All IP ADD CIDR for DB Security Group:

If CIDR/IP :O.0.0.0/0 Not Working then Try

CIDR/IP: 1.1.1.1/32

If 0.0.0.0/0 doesn't work you can try:

0.0.0.0/1 
128.0.0.0/2
192.0.0.0/3
224.0.0.0/4

0.0.0.0/0 does the trick on the EC2 firewall settings

A CIDR defines a range of IP addresses. In the CIDR notation above, /0 is saying "every possible IP".

I like using http://cidr.xyz/ to visualize the range of addresses.

I'm not familiar with how one configures DB Security Groups, but if you allow access from IP's in this range, you'll allow access from any IP (...): 0.0.0.0/0 ...

From a security perspective, you should not do this. You should authorize the smallest possible group. For example, if only the last portion of your IP changes, e.g. your IP is always 1.2.3.*, then authorize 1.2.3.0/24.

For more information about CIDR notation, drop by Wikipedia: http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing