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I'm starting to get emails from various services of this kind:

Your gitlab.com account was signed in to from a new location
 
Hostname    gitlab.com
IP Address  2001:db8:bbbb:1:cccc:dddd:eeee:ffff
Time    2020-10-30 4:32:20 PM UTC

In the old days, when it was just IPv4 I would recognise my own IP-address fairly quickly. This kind of notification are a lot less helpful.

Are there any tricks to find out if the IPv6 address is mine?

Is there any systematics (patterns) to IPv6 addresses that might help?

Tero Kilkanen
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Mausy5043
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    As of 2020, [the first 64 bits *typically* uniquely identify your uplink](https://serverfault.com/questions/426183/how-does-ipv6-subnetting-work-and-how-does-it-differ-from-ipv4-subnetting/426207#426207) so you just need to remember the first half, whereas the second half depends on whatever router manages (or leaves management to clients) your local network. – anx Oct 31 '20 at 15:13
  • @RonMaupin TIL. Was not aware of that. Thanks for the info. – Mausy5043 Nov 01 '20 at 14:32

1 Answers1

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Your ISP will delegate a prefix for you, probably /48 for your business, unless you have a contract that specifies a different size. For example, 2001:db8:cafe::/48. You will then break that prefix into separate /64 networks. For a /48 prefix, that means you can have 65,536 different /64 networks: from 2001:db8:cafe::/64 to2001:db8:cafe:ffff::/64.

It is pretty easy to see which networks belong to you. If any of the first 48 bits delegated to you are different, e.g. 2001:db8:beef::/48, then you would see that addressing does not belong to you.

With just a couple of exceptions, You will use /64 networks for your IPv6. You could further subnet one or more of your /64 network to /127 for point-to-point links (prevents ping pong attacks) or /128 for things like router loopbacks.

Ron Maupin
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