How, sitting behind the provider's nat, does the requested info from the Internet know the exact client's network?

Question

Computer networks

I am sitting at the nat of the provider, I wonder how, if a whole bunch of people like me are given a fixed number of IPs and they are distributed when someone accesses any resource on the Internet in turn, the one from whom I request information , knows which of the bunch of other clients this call belongs to? For example, IP bans, how does the server understand that it is specifically forbidden for computers from my network to access the server, because it is provided with one of the other addresses that can be issued to a completely different person?

Answer 1

which of the bunch of other clients this appeal belongs to

The router has a NAT table in which it recognizes the correspondence SRC_IP: SRC_PORT -> DST_IP: DST_PORT.

how does the server understand that it is specifically forbidden for computers from my network to access the server

On the Internet, IP addresses from the local network are not routable. If banned by IP into which addresses from the local network are pulled, then the entire local network will be banned.

Answer 2

When you are behind a provider, the external service can only know the address from which you actually access the Internet, i.e. external NAT address.
An external service can block this address. Then all your NAT neighbors will automatically be blocked.
Another point: the provider has a pool of white addresses from which clients can access the Internet. The pool can have several subnets assigned to the provider.
Information about provider subnets is publicly available on the Internet. It can be obtained through whois services, etc.
So having received one address, the service can find out the entire subnet of the provider and block it all.

Answer 3

Because the nat technology also transfers all the information about the internal network to the server. Everything is simple.