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by codetrotter 694 days ago
I’d pick the one that supports IPv6 and then make two separate requests to it. One request over IPv4 and one over IPv6.

  curl -4 https://www.cloudflare.com/cdn-cgi/trace

  curl -6 https://www.cloudflare.com/cdn-cgi/trace
Also the reason that the 1.1.1.1 one shows only IPv4 address is because 1.1.1.1 is itself an IPv4 address. So any connection to it will have to be using IPv4.
1 comments
tcfhgj 694 days ago
could you not retrieve your ipv6 directly from the system?
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codetrotter 694 days ago
Yes, but getting it in a response from an external server means I don’t have to be specific about which interface to get the IPv6 address of and so on.
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tcfhgj 694 days ago
the same specific interface used to contact the external server
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codetrotter 694 days ago
Which is neatly abstracted away so you don’t have to think about it unless you want to. And therefore reaching out to an external server and having it say where the request came from is the path of least resistance for a script that can work across different hosts with minimal machine specific configuration.

Listen, if you want to check the IPv6 address from the interface list go ahead I’m not trying to stop you.

But because I anyway need to reach a third party to know my own IPv4 address then yeah when that third party can also tell me IPv6 address I’m gonna do it that way.

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graton 694 days ago
That requires running it on the router/device which gets the public IP address. By using the service you can update your DNS IP address on a system that is behind the router.
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tcfhgj 693 days ago
What do you mean?

Every device gets a public ipv6 (usually).

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graton 693 days ago
I have a router connected to the internet, it gets the public IP address.

The router is connected to the internal network in my home and has the IP address of 192.168.1.1.

Behind the router is my computer which has a non-public IP address, for example 192.168.1.2. My computer is the one I want to run the program to update the DNS entry. My computer does not know what the public IP address is by looking at its interfaces.

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wizzwizz4 694 days ago
i.e., an arbitrarily-selected interface capable of reaching Cloudflare.
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