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Well the 192 case would probably have an external IP + Port uniquely mapped to it in the router’s NAT table. I think you’re missing the larger point though. No

by rand_r 2y ago

Well the 192 case would probably have an external IP + Port uniquely mapped to it in the router’s NAT table. I think you’re missing the larger point though. No one said IPs are exclusively used as GUIDs. Just that they are used as GUIDs, which they are in the majority of cases, and those GUIDs are re-assigned over time. 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.

vel0city 2y ago
> would probably have an external IP + Port uniquely mapped to it in the router’s NAT table. Only on really crappy NAT implementations. My home router can have hundreds of thousands of NAT states, and yet there are only ~61k high number ports. How do you think that works? Because it is not just "external IP at this port goes to this LAN host". Its the whole session information, SRC_PORT, DEST_PORT, SRC_IP, DEST_IP, all get figured into it. At this moment there are several NAT states in my home router that share the same public IP:PORT combination, going to different LAN IP:PORT combinations. An IP address is not globally unique. An IP:PORT is not globally unique. Treating them as globally unique shows a misunderstanding of networking concepts. They're often unique to a single host, but that's not a requirement. Once again, do you really think there's a single network adapter out there that has 8.8.8.8:53?