This is absolutely an issue with Xbox Live/Sony PSN or RBLs used by mail servers for reputation purposes. For better or worse these systems equate one IPv4 address == one user (and possibly one IPv6 /64 == one user). My opinion is that this may be a reasonable or "good enough" assumption as long as you put a time limit on the assumption (so dynamic addresses can be reassigned) and have a rough idea of what a user means (a household, subscriber circuit, or similar). But it obviously goes out the window if you have 10 or 20 unrelated subscribers (possibly in different towns) sharing a single IP address in a 1:many NAT. This may be one of the not-so-obvious support costs that comes up when one decides to run a CGN.

Mike Lewinski wrote on 11/21/2019 11:05 PM:

Question: is anyone who is currently suffering this issue also doing 1:many NAT? Or running a proxy server that might cause multiple clients to all appear from the same IP address? I believe NAT might be the cause of one of our customer's complaints wrt content provider blocking.