How many computers can have the same public IP?

Solution 1:

There is no limit to the number of computers, however there is a limit to the number of simultaneous connections because of the possibility of ephemeral port exhaustion. More computers usually means more connections so there is a practical limit to how many computers will typically share the same IP address. Usually with a very large number of computers, multiple IP addresses will be shared in a pool to be used for NAT.

Solution 2:

As many as can dance on the head of a pin - Or more accurately as many as an administrator wants to hide behind NAT.

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Solution 3:

Besides NAT, they could be behind a proxy. if the proxy is nice to you, you might find more informations in the HTTP-Headers of the requests. Look for X-Forwarded-For headers, which might help you to get closer to your real usercount.

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Solution 4:

Even better, you could have a single computer behind a corporate gateway use a different IP on each hit, because of a load-balancing reverse proxy. Don't use IP as identifier. Just don't.

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Solution 5:

It's fairly typical for an ISP to give a customer just one IP address. In order for a router to allow multiple users on a private network to utilize this address it uses NAT (Network Address Translation).