4 LESSON Understanding Internet Protocol OBJECTIVE DOMAIN MATRIX SKILLS /C ONCEPTS MTA E XAM O BJECTIVE MTA E XAM O BJECTIVE N UMBER Working with IPv4 Understand IPv4. 3.2 Working with IPv6 Understand IPv6. 3.3 KEY TERMS anycast address logicallo gical IP addressadd re ss Automatic Private IP Addressing (APIPA) loopbacklo op ba ck IP addressad dr ess broadcast address masked classful network architecture multicast address classless inter-domain routing (CIDR) multicasting default gateway network address translation (NAT) DNS server address node dual IP stack port address translation (PAT) dynamic IP address private IP addresses global routing prefix public IP addresses interface ID static IP address IP conflict subnetting IPv4 TCP/IP IPv4-mapped addresses truncated IPv6 unicast address IPv6 subnet unmasked IPv6 tunneling variable-length subnet masking (VLSM) 68 Understanding Internet Protocol | 69 As a network administrator, you will use the Transmission Control Protocol/Internet Protocol ( TCP/IP ) communications protocol suite most often. Most techs refer to this simply as Internet Protocol or IP. Although the newer IPv6 has many advantages over its predecessor, IPv4 is still used in the majority of local area networks. In this lesson, we will cover both. To truly be a master of IP networks, a network administrator must know how the different versions of IP work and how to configure, analyze, and test them in the GUI and in the command line. By utilizing knowledge about IP classes and reserved ranges, a well planned network can be implemented. And by taking advantage of technologies like network address translation and subnetting, a more efficient and secure network can be developed. Finally, by incorporating IPv6 whenever possible, you are opening the door to the future of data communications and enabling easier administra- tion, bigger and more powerful data transmissions, and a more secure IP network. To return to our ongoing example, say that Proseware, Inc., expects its network admin- istrators to be able to set up a fully functional IPv4/IPv6 network. In this lesson, we will discuss how to enable computers on the LAN or the Internet to communicate through layer 3 IP addressing. By the end of the lesson, you will be able to configure advanced IP network connections on LANs, WANs, and the Internet. I Working with IPv4v4 Internetrnet ProtocolP ro toco l versionve rsio n 4 or IPv4IP v4 isi s theth e mostmo st frequentlyf re qu en tly usedus ed communicationsc om protocol. IP resides on the network layer of the OSI model, and IP addresses consist of four numbers, each between 0 and 255. The protocol suite is built into most operating systems and used by most Internet connections in the United States and many other countries. As mentioned in Lesson 1, it is composed of a network portion and a host portion, which THE BOTTOM LINE are defined by the subnet mask. In order for an IP address to function, there must be a properly configured IP address and compatible subnet mask. To connect to the Internet, you will also need a gateway address and DNS server address. Advanced examples of IP configurations include subnetting, network address translation (NAT), and classless inter- domain routing (CIDR). Categorizing IPv4 Addresses CERTIFICATION READY IPv4 addresses have been categorized into five IP classes. Some have been reserved for How do you categorize private use, whereas the rest are utilized by public connections. This classification system IPv4? helps define what networks can be used on a LAN and what IP addresses can be used on 3.2 the Internet. The IPv4 classification system is known as the classful network architecture and is broken down into five sections, three of which are commonly used by hosts on networks—Classes A, B, and C. All five sections are displayed in Table 4-1. The first octet of the IP address defines which class the address is a member of. 70 | Lesson 4 Table 4-1 IPv4 classful network architecture IP R ANGE D EFAULT S UBNET N ETWORK /N ODE T OTAL N UMBER T OTAL N UMBER OF CLASS (1 ST OCTET ) M ASK P ORTIONS OF N ETWORKS U SABLE A DDRESSES A 0–127 255.0.0.0 Net.Node.Node.Node 2 7 or 128 2 24 – 2 or 16,777,214 B 128–191 255.255.0.0 Net.Net.Node.Node 2 14 or 16,384 2 16 – 2 or 65,534 C 192–223 255.255.255.0 Net.Net.Net.Node 2 21 or 2,097,151 2 8 – 2 or 254 D 224–239 N/A N/A N/A N/A E 240–255 N/A N/A N/A N/A Class A network addresses are used by the government, ISPs, big corporations, and large uni- versities. Class B network addresses are used by mid-sized companies and smaller ISPs. Class C network addresses are used by small offices and home offices. In the table, ththee tetermrm nonodede is sysynonymousno nymous with “host.“host.” If an IP address is Class A, the first octet is consideredde re d to bbee ththee “n“network”et wo rk ” poportion.rt io n. TThehe ootherth er tthreehr ee ooctetsct ets araree then the node or host portion of theth e address.ad dr es s. So,S o, a computerc om pu te r mightmi gh t be ono n theth e 11 networkn et wo rk anda nd have an indi- vidual host ID ofo f 38.250.1,38 .2 50 .1 , makingma ki ng the entiree nt ir e IP addressa dd re ss 11.38.250.1.1 1. 38.2 50 .1 . In lookingl at the table, you might alsoso haveh av e noticednoti ce d a pattern.pa tt er n. InI n particular,pa rt ic ul ar , ClassCl as s B addressesad dr es se s use twotw octets as the network portion (e.g., 128.1). The other two octets are the host portion. Meanwhile, Class C addresses use the first three octets as the network portion (e.g., 192.168.1). Here, the last octet is the host portion. There are several other notations we need to make to this table. First, as shown, the range for Class A is 0–127. However, the 127 network number isn’t used by hosts as a logical IP address. Instead, this network is used for loopback IP addresses , which allow for testing. For example, every computer that runs IPv4 is assigned a logical IP address such as 192.168.1.1. However, every computer is also automatically assigned the address 127.0.0.1, and any address on the 127 network (for example, 127.200.16.1) redirects to the local loopback. Therefore, this network number cannot be used when designing your logical IP network, but it can definitely be used to aid in testing. Second, as you look at Table 4-1, note the default subnet masks for each class. Notice how they ascend in a corresponding fashion to the network/node portions. Memorize the default subnet masks for Class A, B, and C. Third, be aware that the total number of usable addresses is always going to be two less than the mathematical amount. For example, in a Class C network such as 192.168.50.0, there are 256 mathematical values: the numbers including and between 0 and 255. However, the first and last addresses can’t be used. The number 0 and the number 255 cannot be used as logical IP addresses for hosts because they are already utilized automatically. The 0 in the last octet of 192.168.50.0 defines a network number, not a single IP address, it is the entire net- work. And 192.168.50.255 is known as the broadcast address , which is used to communicate with all hosts on the network. So, because you can never use the first and last addresses, you are left with two fewer addresses—in this case, 254 usable IP addresses. This applies to big- ger networks as well. For instance, a Class A network can use 16,777,214 addresses instead of 16,777,216. If we examine this more carefully, we will see that the number zero in binary equals 00000000 and the number 255 in binary is 11111111. Thus, we can’t use the “all zeros” octet and the “all ones” octet. This rule applies to total hosts, but not to total networks within a particular class. We build on this concept in the subnetting section later in this Understanding Internet Protocol | 71 lesson. One other related notion is the network 0, which generally isn’t used but is listed in the table because it is technically considered part of Class A. Next, Class D and Class E are not used by regular hosts. Therefore, they are not given a network/node classification, and as a result of that, they are not given a specific number of networks or total hosts they can utilize. Instead, Class D is used for what is known as multicasting—transmitting data to multiple computers (or routers). Class E was reserved for future use, but this has given way to IPv6 instead. Finally, try to get into the habit of converting IP octets into their binary form. For example, the binary range of the first octet in Class A (0–127) is 00000000–01111111. For Class B, it is 10000000–10111111, and for Class C, it is 11000000–11011111. To practice doing this, you can use one of many decimal-to-binary conversion methods (such as the one shown in Table 4-2), or for now, you can use the scientific calculator in Windows by navigating to the Run prompt and typing calc.exe .