Possible Duplicate:
Fastest method to determine my PC's IP address (Windows)

I'm not sure the title of my question is appropriate, and I'm not sure my question is going to be appropriately worded. I've just started reading about IP addresses, and I'm very confused about many things so I will probably make some mistakes. I just hope it's going to be comprehensible.

I've learned that at least some of the IP addresses I can see when I type ipconfig into my command line are local, that is they are useless to people and things trying to contact my devices. They are only useful for my devices to communicate with one another. Then there apparently is something called NAT that creates a single IP address that the outside world can use to communicate with my home network. Is it possible for me to find out what this number is?

I've learned that there are two kinds of IP addresses: private and multicast. I understand that the IP address of my computer I can learn by using ipconfig is a private address. Is the address produced by NAT a multicast address?

One of the numbers ipconfig outputs is "default gateway". If I understand correctly, it is the IP number of my router. Is it the number produced by the NAT thing, or is it also a local number? If it's the first, then I think the answer to my previous question must be "no" because this number is not in the multicast address range of IP addresses.

  • ifconfig.me/ip – Rob Aug 14 '12 at 19:23
  • @soandos I'm not asking for the fastest method to determine my IP address. Rather, I wanted to ask for an explanation of the several related things I mentioned. As I said, my title may be inappropriate. Please feel free to edit it -- I'm still thinking about a better one. – Michał Masny Aug 14 '12 at 19:40

I think you are very confused.

  • You can find out your public IP using the answers to this question
  • "I've learned that there are two kinds of IP addresses: private and multicast." Not sure where you heard this, but its wrong. Multicast has to do with sending a message to more than one server. Private IP addresses are the reserved block which are always local
  • Default gateway is a local address, not a public one

The "NAT thing" is Network Address Translation and in the sense that you care about, it figures out how when someone wants to send information to you and you buddy, both of whom are on the same network, which one of you the third party wants to reach.

  • OK, thank you. I would like to ask one more thing. It seems to me that the question you linked to is about finding out the local address of a computer. But Nate Koppenhaver seems to be talking about the public address in his answer. Is this answer misplaced? Or am I misunderstanding something again? – Michał Masny Aug 14 '12 at 20:03
  • Oh, sorry, I think there's more I don't understand. Does NAT produce an individual number for each of the computers on the network, or is it just one number for the whole network? – Michał Masny Aug 14 '12 at 20:09
  • NAT = Router for your purposes. It has just one number for the whole network facing the world, and internally, it has lots of numbers. The question I linked to is about finding the external IP, not internal – soandos Aug 14 '12 at 20:14
  • I see. I think what confused me was that the asker described what ipconfig does on his Windows 7, which seems to be different from what it does on XP. I've been trying to find out if it's possible to see the external IP via ipconfig on XP, and it seems it's not. Is that correct? – Michał Masny Aug 14 '12 at 20:32
  • I believe so, but I don't have access to XP, so I am not sure – soandos Aug 14 '12 at 20:34

The following links each do the same thing. They will print your public facing IP address in an otherwise blank webpage.




  • Thank you. So it's different from the address of my router. But it doesn't seem to be in the range of multicast addresses. Why is that? Does it mean that this is not a unique number? – Michał Masny Aug 14 '12 at 19:26
  • Your home network uses IP addresses from the private IP address space (more info here, en.wikipedia.org/wiki/Private_network). From this address space the most commonly used would be Your router does the same thing. You probably even connect to its remote management via this private ip. For the internet you must have an IP address from the public address space. This is the IP address you see when using the tools I mentioned. This is the IP address your ISP exposes. – Jorge Ferreira Aug 14 '12 at 19:32
  • Oh, so multicast and public don't mean the same thing! That clarifies a lot, thank you. – Michał Masny Aug 14 '12 at 19:37

Not the answer you're looking for? Browse other questions tagged or ask your own question.