To find out the total number of subdivisions or subnet IDs you can have in your net-

Understanding Internet Protocol | 81 As you can see, there are 16 values in each subnet host range, but you can’t use the first and last because they are all 0s and all 1s, respectively. So for example, in Subnet ID 1, the 16 and the 31 are unavailable; 16 is the actual subnet ID, and 31 is the broadcast address for that subnet. The usable IP addresses in that subnet are 17–30. In subnet ID 2, 32 and 47 are unavailable; therefore, the usable range is 33–46. Keep in mind that comput- ers in different subnets cannot communicate with each other by default. So, the IP address 192.168.50.17 cannot communicate with 192.168.50.3,3 and vice versa. Another item of note is that most operating systems including Windows either discourage, or flat out don’t allow, use of the first and last subnet IDs. This is to avoid confusion with the main network number prior to subnetting and the broadcasting segment. That was a lot of information. So, the best way to really explain the subnetting process is to do it. SUBNET A NETWORK GET READY. Let’s create a working subnet. Use the following information to create your working subnetwork: • Network: 192.168.50.0 • Subnet mask: 255.255.255.240 • Subnet ID to be used: ID 7 1. Go to the first computer we will call this computer1.

2. Disable any secondary network adapters. Make sure only one adapter is enabled; this

is the one you will use for the exercise.

3. Access the IP Properties window of computer1 and change the IP settings to reflect

the supplied subnet information. If you look back at Table 4-5, you will notice that subnet ID 7 dictates that you can use IP addresses between 192.168.50.112 and 192.168.50.127. However, remember the “golden rule”: You cannot use the first and last addresses. This means you are left with just 113–126. You can use any of these IPs as long as no two computers get the same IP address. For the purposes of sim- plicity, we chose the first valid IP for computer1, as shown in Figure 4-8. No gateway address or subnet mask is necessary. Be sure to write this out on paper as you go through the exercise. TAKE NOTE Figure 4-8 IP properties of computer1

4. Click OK for both windows.

5. Go to a second computer; we will call this computer2.