First let us understand how to indentify our IPs i,e both internal (private) as well as external (public).
Note: The
terms private (internal)
and public (external)
addresses are also used
To know
you internal IP:
 |
| Go to command prompt. Enter 'ipconfig'. IPv4 Address is your internal/private IP address |
To know
your external IP:
 |
| Many websites are available to identify your external IP. Websites like whatismyipdotcom/myexternalipdotcom/whatisdotcom will provide your external IP |
If you see
both the pictures, my IPs are different.
Internal
IP
|
192.168.0.103
|
External
IP
|
101.56.14.56 |
It
seems that I have two IP addresses, and as a matter of fact I have. The command
‘ipconfig’ shows me my
internal address, and this address is used on my local internal network
But when I ask Google about my IP address I get the
public address which is in fact the external address of my router.
The
reason why we seem to have two IP addresses is because of limited availability of IP addresses
in IPv4 version. The reason that IPv4 is still sustained is a technique called NAT (network address translation).
NAT allows
thousands of computers on an internal network access the internet using a
single external IP address.
An external IP address is
the address assigned to us by our ISP Internet
Service Provider.
Below
graphical presentation will make things easier for you:
In the above picture, router assigns
internal/private IP address to all computers in local network. When any computer wants to connect to internet, external IP address provided by ISP is used. The ISP is
connected to the router and gives the router an external IP address that allows
it to communicate with the internet. While on the internet everyone sees your
external IP address, but any information coming from the router is routed from
the external IP address to the internal IP address.
In this case, there cannot exist two
computers with the same public IP address all over the internet.
A external/public IP address can be either static or dynamic. A static public IP
address does not change and on the
other hand a dynamic public IP address changes each time one connects to
the internet.
Most Internet users will only have a dynamic
IP assigned to their computer which goes off when the computer is disconnected
from the Internet. Thus when it is re-connected it gets a new IP.
The Internet Assigned Numbers Authority
(IANA) has reserved the following three blocks of the IP address space for internal/private networks
(local networks):
10.0.0.0
- 10.255.255.255 (Total Addresses:
16,777,216)
172.16.0.0
- 172.31.255.255 (Total Addresses:
1,048,576)
192.168.0.0 - 192.168.255.255 (Total Addresses: 65,536)
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