Computer IP address question?

Question

Can someone explain to me the difference between the IPv4 IP address and the IP address that a site like www.whatismyipaddress.com would display that my system has? Just a silly computing question that I was curious about. I don't quite understand how a computer is assigned an IP address. Thanks guys =)

Answer 1

Just to keep it as simple as possible. IP stands for Internet Protocol, and IPv4 merely means Internet Protocol Version 4. IPv4 consists of 4 x 8 bits blocks like xxx.xxx.xxx.xxx. So IPv4 is merely a protocol standard to uniquely identify each computer on a network communicating with this protocol (computers can connect with each other in many ways, but TCP/IP is the protocol used widely on the internet - much like languages in various countries, but English is the widely chosen business language).



You've heard much about internal IP addresses within your own subnet assigned by your router, and the IP address issued by your ISP to uniquely identify you on their network, so I shan't go in that.



How a computer is assigned an IP address is most commonly done by DHCP (Dynamic Host Control Protocol). The router or server maintains a list of IP addresses in its database that it can lease out randomly to any user. For instance, when you connect to the ISP, your computer will be assigned an IP address by the ISP. The same IP address may be assigned back to you if that lease hasn't expired. The lease period is determined by the ISP, which can vary from 24 hours to days depending on the number of subscribers the ISP has, and the size of the pool of IP addresses.

Answer 2

Nearly every device that is connected to the Internet has an IP address. There are a few devices which function as passthrough that do not have an IP address, but 99% of Internet users will never come in contact with one of those devices, so let's pretend that they do not exist for the moment.



Therefore, your computer has an IP address which uniquely identifies it within some particular scope. In this case the scope is your local network....maybe a WiFi connection to your house, or an ethernet connection in your office, etc. In any case your IP address associated with your computer has a local scope. Your local network is connected to the Internet using a router. A router is a network device used to connect one network to another. The router has its own IP address. In addition to the router, there will be a modem (note, many ISPs provide devices which bundle the router and modem and often a switch into the same device, but each device type must be present regardless of whether you have 1 box sitting beside your computer or three). The modem which is assigned an IP address by your ISP is your local network's interface to your ISPs network. You may have heard the term, Wide Area Network or WAN. From your standpoint, the LAN is your local network, and the WAN is anything on the other side of the device provided by your ISP.



Remember, I said your computer's IP address has local scope. In other words, only things on your local network can see your computer's IP address. The modem provided by your ISP has a scope of within the ISP's network. But, the ISP uses one of those network devices which does not have its own IP address to deliver an external IP address with global scope to your ISP provided modem. This means that your modem's external IP address truly is in the global scope.



Websites like WhatIsMyIPAddress.com can only "see" network devices with global scope. In other words, they can only "see" your ISP's external IP address associated with your connection. And that's what they report back to you. So you see a different IP address than the one assigned to your computer within your network.



Clear as mud?

Answer 3

You mean the IP address your computer tells you that you have (like 10.0.*** or 192.168.0.*)?



The 192.-address is something called local IP addresses.



When you connect your computer to the router / swtich - the computers in the network are assigned specifik IP-Addresses. Such as 10.* or 192.168.*.



While the external IP address is the one found on whatsmyip.com.



The external IP is the one the websites see, while the local ones are - local.

Only computers on your network see them.