Access the Local Area Connection Properties dialog box. Click Internet Protocol Version 4, then click the Properties button. This displays Click the Use the following IP address radio button. This enables the other fields so Click OK. Then, in the Local A

Understanding Internet Protocol | 73 b. Ping the other computer. Also try to ping any other computers that were con- fi gured as part of this Class A network for example, ping 10.0.0.2. Make sure you get replies. If you do not, check the IP confi gurations of both computers. Also make sure the computers are physically connected to the same network. In addition, as mentioned in previous exercises, verify that fi rewalls are disabled if necessary. Furthermore, it is important to avoid an IP confl ict. IP confl icts occur when two computers are confi gured with the same IP address. If this happens, a small pop-up window at the lower right of your screen will alert you, as shown in Figure 4-2. When confi guring computers statically as we are in this exercise, it is all too easy to become confused as to which computers have which IP addresses. Consider labeling every computer you work on with a different num- ber; computer1, computer2, and so on. Use that number as the last octet of the computer’s IP address in each exercise. This will help reduce your chances of an IP confl ict. Figure 4-2 IP conflict pop-up window CONFIGURE CLASS B ADDRESSES GET READY. In this exercise, you will configure two computers with Class B IP addresses, then verify the configuration through the use of ipconfig and ping: 1. Access the Local Area Connection Properties dialog box.

2. Click Internet Protocol Version 4, then click the Properties button. This displays the

Internet Protocol Version 4 Properties dialog box. Write down the current settings so that you can return the computer to these settings at the end of the exercise.

3. Click the Use the following IP address radio button. This enables the other fields so

you can type in the IP information. Enter the following: • For the IP address of the fi rst computer, enter 172.16.0.1. • For the IP address of the second computer, enter 172.16.0.2. • For the Subnet mask of both computers, enter 255.255.0.0. • Leave the Default gateway and the Preferred DNS server fi elds blank. • When you are fi nished, the fi rst computer’s confi guration should look like Figure 4-3. • If you have other computers, try confi guring their IP addresses as well; the host portion of the IP should ascend once for each computer: .3, .4, .5, and so on. Figure 4-3 IPv4 Properties dialog box using a Class B IP address 74 | Lesson 4 4. Click OK. Then, in the Local Area Connection Properties dialog box, click OK. This will complete and bind the configuration to the network adapter.

5. Now it’s time to test your configuration. We will do this in two ways, first with the

ipconfig command, and second with the ping command: a. Type ipconfi g. Verify that the IP confi guration is accurate and corresponds to what you typed in the IP Properties window. If not, go back and check your Internet Protocol Properties dialog box.

b. Ping the other computer. Also try to ping any other computers that were confi g-

ured as part of this Class B network for example ping 172.16.0.2. Make sure you get replies. If you do not, check the IP confi gurations of both computers. Also make sure the computers are physically connected to the same network. IPv4 addresses are further classified as either public or private. Public IP addresses are ones that are exposed to the Internet; any other computers on the Internet can potentially commu- nicate with them. Private IP addresses are hidden from the Internet and any other networks. They are usually behind an IP proxy or firewall device. There are several ranges of private IP addresses that have been reserved by the IANA, as shown in Table 4-3. The majority of the other IPv4 addresses are considered public. Table 4-3 Private IPv4 addresses as assigned by IANA C LASS S TART OF R ANGE E ND OF R ANGE A 10.0.0.0 10.255.255.255 B 172.16.0.0 172.31.255.255 C 192.168.0.0 192.168.255.255 The only private Class A network is 10. However, there are multiple Class B and C private net- works. 172.16, 172.17, and so on through 172.31 are all valid private Class B networks. And 192.168.0, 192.168.1, 192.168.2, and so on all the way through 192.168.255 are all valid pri- vate Class C networks. Remember that for an address to be Class C, the first three octets must be part of the network portion; for Class B, the first and second octets; and for Class A, only the first octet. Another type of private range was developed by Microsoft for use on small peer-to-peer Windows networks. It is called APIPA, which is an acronym for Automatic Private IP Addressing. It uses a single Class B network number: 169.254.0.0. If a Windows client cannot get an IP address from a DHCP server and has not been configured statically, it will auto- assign a number on this network. If, for some reason, APIPA assigns addresses even though a DHCP server exists, APIPA can be disabled in the registry. See the Microsoft Support site for details. Although most people understand the difference, it would be wise to revisit the topic of static versus dynamic IP addresses. All of the exercises we have done in this lesson have been exam- ples of setting up a static IP address. But most commonly, computers are set up to obtain an IP address and other IP information automatically. In this example of a dynamic IP address, the computer broadcasts out to the network in an attempt to find a DHCP server, whether it’s a 4-port SOHO router, DHCP server, or other appliance. The server then replies with the required information. This is actually accomplished through a four-step process known as DORA that we will cover in more depth in Lesson 6, “Working with Networking Services.”