Internet IP vs. Local IP

[AboveTheLogic]

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 Subnetting, 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 "Network Address Translation", or "NAT".

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 Router does.

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 Internet Service Providers, or "ISPs".

[wimiadmin]

This should keep you busy.

http://en.wikipedia.org/wiki/IP_classes

[acidsatyr]

I'm confused about another thing - in my case, my home address, i.e router, doesn't have public ip address in the first place, that is, my ISP has set up a NAT router for its customers and so we all share one public ip address. Meaning i already have private ip address. As you can imagine not being able to initiate direct conversation with someone from internet sucks.
But thats not the issue here.
What i can't figure out is this:

What is my private ip address in this "behind the NAT private network"? Sites will only register my ISP router's address obviously. When i do ipconfig /all in Windows, i get the address of 192.168.0.2 (my computer), and 192.168.0.1 which is my router. Now, is this NAT behind the NAT? In other words, this is my private ip address (192.168.0.2) which was created by my router? And if so what is my ip address in this private network that ISP created.

Another question about NAT. Can i create NAT inside NAT? In other words, can i take a private address and subnet it furthur? And then take one of those addresses and then subnet it furthur, etc etc.

This is the thing that confuses me so if anyone could help id be greatful!

[AboveTheLogic]

your IP of 192.168.0.2 and the router's IP of 192.168.0.1 are likely both on your same local network

if you look at your router, it probably has 5 ports: "1-4" and "Internet"

the "Internet" port would likely be assigned the Internet IP (that you would see when you visit whatismyip.com), and the 1-4 ports (as well as any wireless devices) would be on the local network, which would be assigned IPs by the router

the router is sharing the "Internet" port connection to all the other devices, which despite all having their own NAT IPs, are sharing the same Internet IP through the router

think of a phone like with multiple extesions... the main phone number is like your Internet IP, and the extensions are like the NAT IPs (192.168.x.x)

this whole process of routing multiple IPs through one gateway (Internet IP address) is what "Network Address Translation" is...

I hope that makes sense

[vic_tagayun]

Hello,

The idea of Public IP (internet) and Private IP (LAN?) is quite confusing. But thanks to the analogy of the pHone extention.
I have few questions though,
1. If all the Pvt. IP can access the internet, will they all have their own unique Internet IP?
-Meaning, if they click on www.whatismyip.com, would they have their own unique IP address?
2. WHen i click on www.whatismyip.com, is it normal that my IP address always changes?

I hope someone can explain to me in an analogy fashion.

[wimiadmin]

Every location that has internet access has an external IP address. Each location might be a home or a business....it depends, but each of them is unique to the net.

And yes....it's normal for your IP to be different each time you visit our site.

[vic_tagayun]

Hello Brian,

Thanks for the reply. My motivation for joining this forum is that our company has s webfiltering scheme, they use "Websense" to filter few websites and even softwares to login like Yahoo Messenger.
I've read one article to setup a server on your home pc by SSH server and connect to this "home" from your work using a software called Putty to bypass Websense or the firewall.
However, by using putty, you need to put the IP address of your home pc. If my home pc's IP address constantly changes, then the connection wont be established at all (I havent tried, but i think there wont be any connection because i observed the hope IP always changes).
Do you know any way to work around this problem?
Thank you.

[wimiadmin]

www.dyndns.org

[johndoe_I_am]

Originally Posted by AboveTheLogic

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 Subnetting, 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 "Network Address Translation", or "NAT".

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 Router does.

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 Internet Service Providers, or "ISPs".

"192.168.0.0 to 192.168.255.255 - Class C"

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

[wimiadmin]

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

Class B ends at 191.255.255.255 and Class C starts at 192.0.0.0

Therefore, 192.168.x.x is a Class C IP address.