What is the difference between 127.0.0.1 and my assigned IPv4 address?

Solution 1:

There's no such thing as "address of the local computer". IP addresses bind with network interfaces. If you have 5 LAN/Wifi cards (network adapters) in your computer then you can have (at least) 5 IPs for those interfaces.

Here what you see is the adapter named "Local Area Connection" with IP address 192.168.1.36, while 127.0.0.1 is the address of the loopback adapter in each PC.

There are many types of IP. Things like 10.x.x.x or 192.168.x.x are private addresses which are used to identify your computer inside the local network. Outsiders cannot see what's inside the local network because they have been hidden after NAT. Each local network will connect with WAN via a router and have a public IP address with the interface facing WAN of the router. If your computer is connected directly to public internet (which is extremely unlikely in an IPv4 network due to the limit in the address range and the high price of static IPs) then you'll have WAN (public) IP address too.

Solution 2:

Your system can have many ip addresses, and many adaptors, physical or virtual.

Typically you have a loopback adaptor (assigned 127.0.0.1, tho there's actually a block of these) and one or a few more.

In this case, Q1: Yes Q2 No

There's a few things that need to communicate internally with a system - a simple example would be that you'd use 127.0.0.1 (or ::1 in ipv6) to access a website running from the same system.

In the typical home network you'd have a single externally routable/non rfc 1918 address ipv4, with NAT being used to send packets to the appropriate internal host, and RFC 1918 addresses allocated to each internal host. Your 192.168.1.X address is unique to your computer in your lan, but not globally. You'd use this to reach your system from computers in your lan, but not externally. If your machine has multiple interfaces, you can tell 'services' to listen to specific ones. In a typical home lan, I might use 192.168.1.1 to contact my router, but this wouldn't work elsewhere. Likewise, I could use 192.168.1.38 from 192.168.1.39 but not outside

If your PC was the only device, directly connected to a modem or similar device (as opposed to a consumer router) or has a public IP address as part of an organization/ISP that has a block of them, and assigns/routes them for you, you'd have a globally routable IP address. My ISP gives me one ipv4 address and a block of ipv6 addresses, with multiple ipv6 addresses per interface.

Where you have multiple interfaces, you could have a mix of private and public IPs - typically VPS providers do this, so you can access another VPS on the same provider without using your external data quota.

All of them are my ip address from different perspectives. My RFC 1918 address is valid from inside my lan, my external ip address with a port forward is valid externally, and my ipv6 address is valid anywhere there is ipv6.

Solution 3:

Question 1:

• The IPv4 address of your computer is, as the ipconfig command reports, 192.168.1.36.
• As for the 127.0.0.1 address, that is what is called a “loopback” address - it is a special IP address that you can send traffic to that will just go right back to yourself.
• As you mentioned, on a typical computer, 127.0.0.1 is the same as localhost. If you open up the C:\Windows\System32\drivers\etc\hosts file in Notepad, you can see where the mapping comes from. (And you can change it if you want, but this generally isn't recommended.)
• What is the loopback address used for? Various things. For example, if you wanted to work on a webpage that you were building but for some reason your computer didn't have any Ethernet or wireless NICs, then you would still be able to get to the website by using a browser to connect to http://127.0.0.1/.

Question 2:

• The 192.168.1.36 IPv4 address is NOT used to uniquely identify your computer to the world. That is your LAN IP address. Only computers behind your router cam directly access your LAN IP address.
• If you want to find the address that uniquely identifies you, simply visit http://www.whatismyip.com/.