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When setting up access control lists, what's the difference between 0.0.0.0/0 and ::/0?

I'm seeing this for an AWS EC2 instance I'm setting up

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0.0.0.0/0 is the IPv4 everything - all possible IPv4 addresses.
::/0 is the IPv6 equivalent of that.

You can, for example, allow IPv4 and disallow IPv6 or vice versa.

@kasperd mentions:

It should be noted that depending on implementation ::/0 can mean either all IPv6 addresses or all IPv4 and IPv6 addresses. That's because IPv4 addresses can be mapped into IPv6 addresses ::ffff:0:0/96

More info on IPv6 is here.

  • 10
    It should be noted that depending on implementation ::/0 can mean either all IPv6 addresses or all IPv4 and IPv6 addresses. That's because IPv4 addresses can be mapped into IPv6 addresses ::ffff:0:0/96. – kasperd Sep 19 '17 at 17:09
  • Any idea in what context EC2 uses it? Would be good to know. – Hassan Baig Sep 19 '17 at 18:42
  • Isn't that just a firewall ? By default everything should be allowed from anywhere. If you remove those rules before adding your public subnets you might loose connectivity to the instances. – bocian85 Sep 20 '17 at 11:26
  • I believe Amazon implementation follows: 0.0.0.0/0 for IPv4 everything and ::/0 for IPv6 – Marco Rivadeneyra Jan 31 at 14:15
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0.0.0.0/0 is IPv4 and ::/0 is the default route address for IPv6 covering all addresses.

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