How many 192.168.1.1 devices are out there? How many different distinct physical boxes respond to traffic going to 1.1.1.1?
The reason it's not unique (using my rudamentry understanding of networking) is because multiple routers can broadcast the same IP so devices can use the closest router.
However I think it's fair to say IP address are intended to be unique to an org while private ips are not.
Sure, but the person I'm replying to wasn't making a distinction here. They're just saying, "Have you ever changed the static IP address of a computer", where does that exclude RFC1918 IP addresses? I'm right for the right reasons IRT to the person I'm replying to. There are IP addresses which are absolutely not globally unique in any way, shape, or form by design.
> I think it's fair to say [public] IP address are intended to be unique to an org while private ips are not.
"Unique to an org", that's massively different from "globally unique" which is what the person I replied to suggested.
> multiple routers can broadcast the same IP so devices can use the closest router.
100% correct here, that's the biggest reason why you'd have an IP address shared among a lot of different devices.
I’ve been working in tech for 20 years, am coming off a year-long sabbatical, and for the past couple of months have been struggling with the feeling that the joy is gone and I should consider a radical career change.
Reading (what feels to me as) the aggressive pedantry of parent commenter in this thread is giving me a straight up anxiety attack. I’m not sure I have it in me anymore to be in meetings with people whose brains work this way.
Is it like this in every industry or is it more concentrated in tech? I don’t know who’s going to see this, but if you have any perspective or feedback you’d like to share, I’m all ears.
There’s exceptions like broadcast IPs, but the point is that it is a system for uniquely locating devices and listening OS processes with IDs routinely shifting around.
So which globally unique box is 192.168.1.1:443? Can you point to exactly one device out there with that IP:PORT combo? There's probably hundreds of millions of that IP:Port combination currently running and listening.
Which globally unique box is 8.8.8.8:53? You think there's seriously just one network adapter listening for traffic at 1.1.1.1:53? These aren't "broadcast IPs".
https://en.wikipedia.org/wiki/Broadcast_address
And even then, "ultimately associated with a single physical network interface on a device" isn't correct either. You can have multiple physical interfaces listening on the same IP and end up with the same ports.
My Macbook Pro currently has unique IP + Port, associated with a single process listening to it over NAT and packets you send are routed to its network interface. Next week, someone else’s laptop could have that same IP + Port. That’s the main idea here, not these exceptions.
if you take someone elses public IPv4 address and they're using it, neither one of you will be functional, and they will come knocking on your door.
Sure, but if I have the IP address 1.2.3.4 I can have lots of unique physical things have that publicly routable IP address and have them all work if I do it right.
