Chapter 5

Need More Addresses? Try Subnetting and NAT

In This Chapter

Protocols in this chapter: IP, DHCP, NAT, NAT-PT

Using IP addresses economically

Understanding subnets and why they wear masks

Letting DHCP do the work and save on IP addresses

Understanding how NAT helps ease an IP address shortage

Drinking in NAT security

Using NAT to move between IPv4 and IPv6

TCP/IP is like a restaurant. When the restaurant runs out of a popular dish, it substitutes another one on the menu. When IP runs out of addresses, it also substitutes other dishes.

The Internet is running out of 32-bit IPv4 addresses! You must have heard that before, maybe many times. But is that shortage still a problem? Maybe not; the TCP/IP restaurant has a delicious addition to the menu: Have a look at IPv6 in Chapter 9 to see how the next generation of IP — and its 128 bits — will hold us for a long time, provide a massive boost in address space, and offer built-in security. Yum. But many organizations and people haven’t moved to IPv6 yet. So, we need some other items on the menu to keep surviving with the limited number of IPv4 addresses still available while the great migration goes on. In this chapter, we describe some ways to conserve IPv4 addresses without giving up any Internet connectivity.

So take heart as you peruse some appetizing subnet techniques and a tasty short menu of protocols to help satisfy the Net’s short-term appetite for addresses.

Working with Subnets and Subnet Masks

Subnets divide one ...

Get TCP/IP For Dummies, 6th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.