I'm going through a networking CBT at work and I have a question. Here's the part I read leading up to my question:

Private IP addresses:
Unlike an Internet host that requires a globally unique IP address, a host on a private network can use any valid address, provided the address is unique within the private network.

Because many private networks exist alongside public networks, the practice of randomly taking any address is strongly discouraged.

Three blocks of IP addresses have been designated for private, internal use – 1 Class A network, 16 Class B networks, and 256 Class C networks. The internal class ranges are as follows:


Class A is from 10.0.0.0 to 10.255.255.255
Class B is from 172.16.0.0 to 172.31.255.255
Class C is from 192.168.0.0 to 192.168.255.255


You can address a nonpublic intranet using these private addresses instead of globally unique IP addresses. However, private addresses cannot be routed on the Internet backbone.

Internet routers are configured to discard packets from private IP addresses. Therefore, to connect a network with a private address to the Internet, the private address must be translated into a public address.

This translation process is referred to as Network Address Translation (NAT), and it is typically performed by a router.


Okay, now my question. What does it matter what range of IP addresses I use on a private network? It's private, so it's not going to conflict with anyone on the Internet. If I need to access the Internet, the IP address being used by my computer will be translated by the router using NAT to a unique public IP address assigned to my organization. Are they saying that the router will only translate the IP address from private to public if I am using a known private IP address for my network? It seems like a router could be configured to recognize any particular range of IP addresses to be private so that it would properly translate them if someone wanted to leave the private network. Thanks.