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So I've portforwarded my machine using the graphical interface provided by my router. This interface also gives me a public IPv6 which I can use to communicate with my machine through the internet. This IP works fine, but when I check my IP on sites such as whatismyipaddress.com, the second half of my address is different. I cannot use the latter IP for communication. Why do those IP sites get the address wrong?

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    Does this answer your question? IPv6 and online privacy and security – Zac67 Aug 18 '20 at 10:24
  • @Zac67 I may have not understood everything, so correct me if I'm wrong, but I don't think this helps. As far as i can tell, it hasn't explained why I get two different IP addresses instead of one IP for my machine. – Jackson Tarisa Aug 18 '20 at 12:34
  • It's absolutely standard for an IPv6 node to use several IP addresses from your allocated prefix (plus local ones), which the linked Q&A is about. Also, your question needs to specify which "IP" (address) you've got problems with, IPv4 or IPv6. – Zac67 Aug 18 '20 at 13:18
  • NAPT port forwarding and firewall rules are two very different things. You do not forward ports for IPv6, but you need to create a firewall rule to allow traffic through. Also, the host may have a firewall enabled on it. – Ron Maupin Aug 18 '20 at 13:28
  • Welcome on StackExchange. The IP address reported by whatismyipaddress.com is correct. These servers don't falsify your IP address. You should use them to debug your portforwarding rewriting your IP and turn it off since you don't need it with IPv6. – dan Aug 19 '20 at 8:46
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With IPv6 there is no need for NAT / port forwarding. The IP address you are seeing is the IPv6 address of the device you are using to access whatismyipaddress.com.

The whole idea of IPv6 is provide (bring back) end to end connectivity. NAT was only created as a short term solution for IPv4 address shortage.

There is no port forwarding for IPv6. There is only a 1:1 NAT which translates one internal address to one external address.

As you wrote

the second half of my address is different

I'd exclude 1:1 NAT from the list of possibilities.

There are three categories of routers:

  1. No IPv6 Support
  2. Allow all IPv6 traffic with out filtering. It may or should be possible to configure filter rules to some degree depending on the model.
  3. Drop all IPv6 traffic an require to manually setup filter rules

Please check the IP addresses on you computer using ip (Linux), ifconfig (Mac), ipconfig (Windows).

You may see multiple IPv6 addresses but one of them should be the address you see on whatismyipaddress.com.

(And please to a fresh check, some operating systems tend to change IPv6 addresses on a regular basis as a default.)

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  • So if I'm understanding correctly, I don't have to port forward, but I do still have to allow access through my firewall. I think I was confusing these things. Regarding the rest of your answer: Does that mean the IP on whatsmyip is the IP of my device and the ip provided by my router is the IP of my router, which then portforwards the data to my machine? The strange thing is, I can't use the IP from whatsmyip to connect to my machine. I have to use the router IP for that. If the IP on whatsmyip IS my device IP, why can't I use it to connect? – Jackson Tarisa Aug 18 '20 at 12:23
  • That depends on the firewall you are using and the setup you are running. Sometimes IPv6 is open to the world sometimes there is a firewall in place. – Jens Link Aug 18 '20 at 12:27
  • I think I'm following what your saying: The IPv6 address that DOES work for communication is the IPv6 of my router which is then redirecting the traffic to the IPv6 of my computer? I'm fairly sure that portforwarding on my router automatically disables the firewall for that specific port and IP as well as actually portforwarding, so the IPv6 of my machine should be visible to the internet should it not? I also don't understand why my router is behaving this way, it's acting like a NAT even though it's using IPv6's. – Jackson Tarisa Aug 22 '20 at 1:04
  • Continuation: It could be because it is still being portforwarded so it thinks it has to act like a NAT. I don't know if I can just turn off the firewall and not portforward it, because as I said, I think those two are linked on my router. Maybe I'm rambling, the point is, I sort of understand why there are two different IPv6's, but I don't understand why they both aren't accessible for communication. – Jackson Tarisa Aug 22 '20 at 1:08
  • Changes the answer. I hope I covered all your questions. – Jens Link Aug 23 '20 at 9:49

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