You've read a lot in the last few chapters about DHCP, and you may be wondering what it really is. As my grandpa would have said, here's the five-cent version.
DHCP (Dynamic Host Configuration Protocol) is an agreed-upon standard for assigning variable Internet Protocol (IP) addresses to devices on a network. These variable addresses are called dynamic IPs.
Dynamic addressing makes network administration easier because the software keeps track of IP addresses rather than requiring a human being to perform the task. It greatly simplifies things to be able to add a new computer to a network without the hassle of manually assigning it a unique IP address. For whatever it's worth, you also don't need to have as many IPs with dynamic IP addressing because not everyone will be on the network simultaneously.
With dynamic addressing, a device can have (and most likely will have) a different IP address every time it connects to the network. In some situations, the device's IP address can even change while it is still connected, for example, when you release and renew your IP settings using Ipconfig, as I explained in Chapter 15.
You may have noticed that so far I've said "a network," not "the Internet." From a conceptual viewpoint, the Internet is just a great, big, fat network. As a general matter, great, big, fat networks are called WANs (or Wide Area Networks). So from one viewpoint, your router is simply performing a gateway function between your local area network (LAN) and the WAN that is the Internet. The DHCP servers provided by your ISP give your router a dynamic IP so that it can communicate with the WAN (the Internet). Within your own network (the LAN), the router assigns dynamic IPs to each node on the private network. Using Ipconfig, as described in Chapter 15, you can see the IP assigned to each of your computers. A technology called Network Address Translation (NAT) allows a single device, such as your router, to act in this way as an agent between the public network (the Internet) and your local, private network. This is what allows a single IP address to represent an entire group of computers.