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Emanuil Rusev
Asked: 2011-09-01 06:13:43 +0800 CST

How many computers can have the same public IP?

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I've got a list of hundreds of page requests from the same IP and I need to know if these could be requests by different computers.

networking nat ip

7 Answers

  1. Best Answer

    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.

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  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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  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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  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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  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).

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  6. Of course they can.

    If you're on a network and you have 1 public IP address, each page request (even if it comes from different computers) still comes from the same IP address.

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  7. There can be any number of computers on a LAN (It may depend on the physical medium used between them i.e. cables, repeaters etc.), normally there is a single Gateway (at least one is required) to connect to the Internet. These Gateways normally have multiple IPs (both private and public) for the communication.

    Now as the LAN can inturn be set of LANs... figuring out the correct client is a herculean task if not impossible... Though you can still get to that by looking to the routing tables of Gateway or by accessing NAT...This Link may help

    Most of the times public IP is used by ISPs and Large or Mid size Organizations... That is why using client IP is not considered a wise idea now a days.

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