If two IP addresses match, then is that the same computer?

Question

I guess to better answer my question...
On a forum I frequent, there are two usernames that have the exact same IP addresses. Is that the same computer and possibly the same person using the two usernames?

Or what detective work would I need to do to figure out if they are the same? :)

Answer 1

what no one seems to understand is that a complete end point ip address consist of ipaddress.port. so if we assume that the addresses you are seeing are in the "public" address space, then you need the ipaddress.port number to determine if the end point is the same. if the ipaddress AND the source port number are the same, AND this is in the public address space, then it's the same end point or computer. of course, then you get into multi-user systems......but thats not too common nowadays.

this is how most Network Address Translation (NAT) systems work. a single public ip address gets mapped to multiple internal private addresses by assigning different port numbers to the outbound connection requests. so a 192.168.1.250 internal source, with a source port of 2113 (for instance) may get mapped to a 63.12.2.1.5776 source address after being NAT'd. the NATing device maintains a table so that when it sees a packet destined for 63.12.2.1.5776 it will translate that address to 192.168.1.250.2113 and forward it. so that 63.12.2.1 address could have thousands of different end points communicating with that source ip address.

Answer 2

Not necessarily. The most common cause of them *not* being the same is if one computer was given an address via DHCP on Monday, and then some OTHER computer got assigned that address on Wednesday. This is why having accurate time/date stamps on logfiles is important - so you can look through the DHCP logs and see who had that address that day.

There are a number of other cases where it's not the same computer (for instance, going to a web server - these are often what are called "load balanced" or "rouond robin" clusters of systems - it's *supposed* to look like "the same system" all the time, but if you have a cluster of 8 or 12 supposedly identical systems, and one breaks, you can end up with something that works 9 or so times out of 10, but fails sometimes. A royal pain to debug.

Bottom line - "same IP" is *not*, by itself, a sufficient to prove it's the same computer - you need more information about the network configuration and so on.

Also, keep in mind that "different IP" does *not* guarantee that it's actually a different computer - my laptop will probably go through at least 6 IP addresses today - and at one point likely be using at least 3 different ones at the same time (don't ask.. :)

Answer 3

Internet today has grown into a very big cyber interconnection beyond anyones imagination .
saying that no two computers can have same ip address is totally false . there are mainly three conditions when two or more computers can have same ip address:
1 when the isp(internet service provider) is not fully fledged one and or provides internet connection wirelessly then there is a possibility that the computers that connect to it will have "shared ip" and any monitoring software will show their ip as one.
2. also when the computer is used via a router or a anonymous or proxy server . in such case the computers connecting to the same proxy server will show the same ip.
3 lastly if the computers are connected on a lan and then connected to the internet via a server then the ip adresses will also be the same
thanks . hope u got it what u wanted to know

Answer 4

No two IP addresses are the same. However, the IP address you are seeing might be that of a router (to which multiple devices connected to that router will appear to have the same IP). That being said, all devices on the same network have unique IPs but the router they are connected to may show up as being only one IP.

Answer 5

Depending... There are some programs that allow a computer to access the Internet anonimus, meaning the servers it accesses won't know its IP address. I don't know how they do that, but they do!
So, if you have two IP addresses and know for shure they are real, if they are the same, yes, it's the same computer

Answer 6

Not necessarliy. My husband and I each have a computer of our own, and both are on the same router (we have a cable modem) and we have the same IP address for two different computers. Hope that makes sense, I haven't had my coffee yet.

Answer 7

If those two users have a dial-up connection and use the same ISP then it it possible that they have the same IP as dial-up user's IP get changed whenever they dial to the internet.

Answer 8

two ips cannot match - impossible. every ip assigned is unique.

Answer 9

s

Answer 10

Do't WORRY, IT WILL NEVER HAPPEN LIKE THAT!