Internet IP vs. Local IP

Steve Bonilla Staff asked 2 years ago

I think there is a great deal of confusion over what IP address you have any how it is used.

Firstly, it is important to understand that there are only so many IP addresses in the world. To truely understand why, you need to understand binary vs. decimal. Binary numbers are simple: 0 and 1. Decimal, however, is 0,1,2,3,4,5,6,7,8,9.

I won't go into too much detail, but an IP address is a decimal representation of your binary address.

The IP address 0.0.0.0 (decimal) = 00000000.00000000.00000000.00000000 (binary)

The IP address 255.255.255.255 (decimal) = 11111111.11111111.11111111.11111111 (binary)

Even with [url="http://en.wikipedia.org/wiki/Subnetwork"]Subnetting[/url], considering there are millions of computers in the world, assigning 1 IP address to every computer and device connected to the Internet in the world will be impossible, we will simply run out!

So, the simple resolution to this is a method called "[url="http://en.wikipedia.org/wiki/Network_address_translation"]Network Address Translation[/url]", or "NAT".

[b]Think of NAT as a phone extension. Your office phone may only have one phone number, but many phones that have extensions. The default phone, your receptionist, answers general requests, and this is what your [url="http://en.wikipedia.org/wiki/Router"]Router[/url] does.[/b]

Depending on the request, your router then forwards the request to the appropriate local machine, using it's local NAT IP address.

Now, you may be wondering if your IP address is a NAT (local) IP, or an external (Internet) IP, an easy way to find out is to look at this:

Private IP Address Reservatiosn
10.0.0.0 to 10.255.255.255 - Class A
172.16.0.0 to 172.31.255.255 - Class B
192.168.0.0 to 192.168.255.255 - Class C

If your IP is in that range, it is likely a private NAT IP. These ranges of IP addresses are excluded from being available to [url="http://en.wikipedia.org/wiki/Internet_service_provider"]Internet Service Providers[/url], or "ISPs".

5 Answers
wimiadmin Staff answered 2 years ago

This should keep you busy. 😀

[URL]http://en.wikipedia.org/wiki/IP_classes[/URL]

johndoe_I_am answered 2 years ago

[QUOTE=AboveTheLogic;427]I think there is a great deal of confusion over what IP address you have any how it is used.

Firstly, it is important to understand that there are only so many IP addresses in the world. To truely understand why, you need to understand binary vs. decimal. Binary numbers are simple: 0 and 1. Decimal, however, is 0,1,2,3,4,5,6,7,8,9.

I won't go into too much detail, but an IP address is a decimal representation of your binary address.

The IP address 0.0.0.0 (decimal) = 00000000.00000000.00000000.00000000 (binary)

The IP address 255.255.255.255 (decimal) = 11111111.11111111.11111111.11111111 (binary)

Even with [url="http://en.wikipedia.org/wiki/Subnetwork"]Subnetting[/url], considering there are millions of computers in the world, assigning 1 IP address to every computer and device connected to the Internet in the world will be impossible, we will simply run out!

So, the simple resolution to this is a method called "[url="http://en.wikipedia.org/wiki/Network_address_translation"]Network Address Translation[/url]", or "NAT".

[b]Think of NAT as a phone extension. Your office phone may only have one phone number, but many phones that have extensions. The default phone, your receptionist, answers general requests, and this is what your [url="http://en.wikipedia.org/wiki/Router"]Router[/url] does.[/b]

Depending on the request, your router then forwards the request to the appropriate local machine, using it's local NAT IP address.

Now, you may be wondering if your IP address is a NAT (local) IP, or an external (Internet) IP, an easy way to find out is to look at this:

Private IP Address Reservatiosn
10.0.0.0 to 10.255.255.255 - Class A
172.16.0.0 to 172.31.255.255 - Class B
192.168.0.0 to 192.168.255.255 - Class C

If your IP is in that range, it is likely a private NAT IP. These ranges of IP addresses are excluded from being available to [url="http://en.wikipedia.org/wiki/Internet_service_provider"]Internet Service Providers[/url], or "ISPs".[/QUOTE]

"192.168.0.0 to 192.168.255.255 - Class C"

FYI 192.168.x.x is a class B not a class C.

westshout answered 2 years ago

Ok, I have read and searched and have found nothing to help me wrap my head around my situation. When I got to WIMI home page its tells me my ip is 64.18... But when I go into my WRT54G [B]"Status"[/B] page it tells me my external ip is 172.16.. I have my router setup to assign my computers in house IPs starting with 10.32.5...

I want to run an FTP and a VNC server to access one of my computers when I'm not home. I have all my port forwarding set up correctly and can access these services from my local machine or other in house computers using both the 172.16.. and the 10.32.5.. addresses.

But when I try to access them (from my own machine) using the 64.18... IP that WIMI says I am I get errors and nothing works.

Is this an example of my PCs being behing my router which is behind another router in place by my ISP? If so, will I ever be able to use these services? How would the ISP router know whish subscriber computer to send the requests to? I can't exactly setup port forwarding on their router...

Maybe I got it all wrong, but I really hope you all can help me. One last thing, I have not been able to test connecting to these services from a true outside computer using either the 64.18 IP or the 172.16 IP.

nightwriter answered 2 years ago

Thanks to this thread's initiator for the clear explanation. Your use of analogies made the concept of public IP versus private IP much easier to understand.
I'm a complete novice when it comes to IT. Frankly, I despair at trying to understand much when conversing with a learned IT person. Most don't seem to be conscious of the fact that they need to explain things VERY simply to novices - we just don't have the basic language. So, thanks!!!
Oh, I do have a question: We have an ADSL modem/router (?), one internet connection, and several PCs connected to this. When I check the IP from any PC, the same IP shows up. Ditto when I check for the private IP. FRom what I understand, each PC should have it's own private IP. Is that correct?
As all PCs reveal the same private IP, won't it appear to websites that we're just one user/person?

Cody Robertson Staff answered 2 years ago

In the early stages of development of the Internet Protocol, network administrators interpreted an IP address in two parts: network number portion and host number portion. The highest order octet (most significant eight bits) in an address was designated as the network number and the remaining bits were called the rest field or host identifier and were used for host numbering within a network.

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