ng a binary system. Similarly, if you need 8 usable hosts on the network, you must provide 16 host addresses, not 8. Figure 34-17 shows the same information as that presented in the preceding work- sheet in a different format. Some people respond better to seeing this information in a horizontal rather than a vertical format-I like this model because it is laid out the same way the bits are laid out in a subnet mask. Use whichever format works for you. There are no tests in this book. 255.255. Subnets Hosts Double numbers in the direction of the arrows Figure 34-17. Horizontal format of the subnet worksheet Chapter 34: IP Design Remember, a proper subnet mask can have only one of nine values in any single octet. If you start with a value of 1 on the bottom left, and a value of 256 on the top right, then double those numbers under each subsequent value, you can quickly fig- ure out what your subnet mask needs to be based on how many hosts it needs to have or how many subnets. Once you have memorized the nine subnet octet values (remember, two are easy!), and can double and halve the rest in your head, you'll find that the numbers become obvious. You'll see all of these numbers over and over if you're around computers for any length of time. They're all powers of two, and when you start to recognize the patterns I've outlined for you, calculating any subnet mask will be an easy matter of doing some quick, very simple math in your head. IP Subnetting Made Easy CHAPTER 35 Network Time Protocol The Network Time Protocol (NTP) is an Internet protocol used for synchronizing a device's clock with a reference source across a network. When accurate time is required on your networking equipment or computers, you should use NTP-in other words, you should always use it. NTP was originally defined in RFC 958. The last documented version is Version 3, which is defined in RFC 1305. To learn more about NTP, check out its home page: http://www.ntp.org. The interesting stuff relating to how NTP really works is found in RFC 1129, wh