Since the host IP address must be unique, the simple rule to calculate the number of hosts for our network is one IP address per host, plus one IP address for each additional net- work adapter in a host machine.We have a concept of one network in the corporate sense, but when determining address requirements, there are a few more details we must consider. You can define IP addresses using one of the three classes available for standard IP communications: Classes A, B, and C. Before we decide which class to use, we need to determine the type of network we are implementing and how many hosts there are per segment. EXAM WARNING You should know the IP address classes and their ranges, the default mask for each class, and the number of hosts each class can support. www.syngress.com 172 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure Figure 3.9 IP City City 192.168.3.1 192.168.3.2 192.168.3.3 192.168.2.1 192.168.2.2 192.168.2.3 192.168.1.1 192.168.1.2 192.168.1.3 192.168.3.0/24 192.168.2.0/24 192.168.1.0/24 192.168.4.0/24 35 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 172 Creating a Subnetting Scheme IP addresses are 32-bit values, often referred to as dotted quads. Each bit is a binary value of either 0 or 1. Since there are 8 bits, there are 2 8 combinations of 0 and 1, which equals 256 combinations, allowing for a range of 0 to 255. An address is broken down into octets con- sisting of four 8-bit sections. An address is usually represented by a decimal number such as 141.59.115.7, which is equal to the binary number of 10001101.00111011. 01110011.00000111. Computers process only binary information, but we convert it to dec- imal because that is easier for us human beings to work with. Classful Addressing As mentioned, host addresses can belong to one of three classes of IP address, and each has a range of addresses.The range is defined by the value of the first octet.Table 3.3 shows the classes and their ranges, as well as the binary representations of the ranges. Classes D and E are also classes of IP addresses, but Class D is restricted to multicasting and Class E addresses are reserved for future use. 127.0.0.0 is reserved for connectivity testing. 127.0.0.1 is a spe- cial address that represents the local loopback adapter that resolves as localhost.We can ping the local host to troubleshoot the protocol stack.We will discuss this in more detail in the “Troubleshooting IP Addressing” section later in this chapter. Each class also has a default subnet mask. Table 3.3 IP Address Classes and Their Ranges Class Range of Values Default Mask Networks Hosts Binary A 0 to 126 255.0.0.0 126 16,777,214 00000001 to 01111110 B 128 to 191 255.255.0.0 16,384 65,534 10000000 to 10111111 C 192 to 223 255.255.255.0 2,097,152 254 11000000 to 11011111 D 224 to 239 Not applicable Not applicable TEST DAY TIP In Table 3.3, notice that the first two bits of the first octet in each class also define the top of the range of network IDs for that class. If you take the first two bits of Class A, 01, and add the remaining six digits as ones you get 01111111, or 127. Remember that 127 is reserved, so 126 is the highest value for the network ID of a Class A network. Class B is 10 (101111111 = 191), and Class C is 11 (11011111 = 223). www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 173 EXAM 70-293 OBJECTIVE 2.1.3 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 173 The default mask for each class defines the number of networks and the number of hosts for each network. An IP address contains information about the network on which the host resides, and the address of the host.The network ID is the reference to the logical subnet, and it refers to the octets that are predefined as the network ID and implemented with the default mask.The remaining octets are for the hosts. Figure 3.10 illustrates the net- work and host IDs. The first address in each network refers to “this network” (itself), such as 24.0.0.0/8 or 204.79.26.0/24.The last address in each network or subnetwork is the broadcast address for that segment, such as 179.54.255.255 or 204.79.26.255.We can derive the formula for determining the number of hosts per network as 2 n – 2, where n is the number of bits available for host IDs. In Figure 3.10, we are using a subnet mask of 255.255.0.0, so the last two octets, or 16 bits, are available. If we plug that into the formula, we get 2 16 – 2 = 65,534 hosts per network. Class A addresses are used for networks that have a large number of hosts. Based on the default mask, we have the first octet for networks and the last three for hosts. So, we have 126 networks and 2 24 – 2 hosts, or 16,777,214. Likewise, with class B, the default mask is 255.255.0.0, so the first two octets are for the network IDs, for a total of 16,384, and the last two are for the hosts. So, class B networks have 2 16 – 2 hosts, or 65,534. Class C net- works have more networks but are smaller, with 2 8 – 2 hosts, or 254. We could implement our network now very simply. Determine the number of hosts and the number of networks, and pick the class that fits. If you do not wish to assign a public IP address to all your machines, there is another solution.There are three banks of IP addresses that are called private IP address ranges.They are listed in Table 3.4.Typically, a net- work will need only one or two public addresses for the Internet interfaces, and everything internal to the company can use the private IP addresses internally. www.syngress.com 174 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure Figure 3.10 Network ID and Host ID 179.86 255.255 2.172 0.0 Network Host ID IP Address Subnet mask 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 174 Table 3.4 Private IP Addresses Network ID Subnet Mask Range 10.0.0.0 255.0.0.0 10.0.0.1 to 10.255.255.254 172.16.0.0 255.240.0.0 172.16.0.1 to 172.31.255.254 192.168.0.0 255.255.0.0 192.168.0.1 to 192.168.255.254 Understanding ANDing and Binary Numbering Once we define our subnetworks, the machines will need to communicate with other machines on the network.The determination of the host as a local or remote destination is derived by applying the subnet mask of the source host to the IP address of the destination. This process involves applying a Boolean logic method called ANDing. By ANDing the binary representation of an address and a subnet mask, the IP layer can determine if the address is on the same logical network or a different one. In Table 3.5, we have a source and a destination host address. First, the subnet mask is applied to the source address using Boolean AND logic.To perform the AND operation, start from the left and compare each bit in the binary numbers representing the IP address and the subnet mask. If both are 1 (1 AND 1), then the result is 1; otherwise, the result is 0. After the comparison is performed with each address, if the resulting binary values are equal, then the addresses are on the same network; if they are not equal, then they are on different logical networks. Table 3.5 Applying the Subnet Mask to IP Addresses Source IP Address 172.16.5.16 Destination IP Address 172.16.2.251 Subnet Mask 255.255.254.0 Subnet Mask 255.255.254.0 10101100.00010000.00000101.00010000 10101100.00010000.00000010.11111011 11111111.11111111.11111110.00000000 11111111.11111111.11111110.00000000 10101100.00010000.00000100.00000000 10101100.00010000.00000010.00000000 We can use the default subnet masks to define our network, or we can use a custom subnet mask.The ability to define the subnet mask allows us to take the default network definition and “borrow” bits from the available hosts on that network in order to create smaller logical networks, or subnets. www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 175 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 175 E XERCISE 3.03 FUN WITH BINARY NUMBERS In this exercise, you will use the scientific mode of Windows Calculator to con- vert binary numbers to decimal numbers and vice versa. 1. Select Start | Run and type calc to launch Windows Calculator. 2. Select View | Scientific. 3. Make sure the Dec radio button is selected. 4. Using the keypad, enter the number 175. 5. Click the Bin radio button. You should see 10101111. 6. In the edit box, type 11000111. 7. Click the Dec radio button. You should see 199. 8. Type 75 in the edit box, and then click the Bin radio button. 9. Notice the binary number is 1001011. Count the number of bits. There are only 7 bits in the result. Calculator will strip leading zeros from binary values, so it is important to always “pad” the binary numbers to 8 bits when using them for IP address functions. The correct represen- tation for 75 as an IP address octet is 01001011. 10. Use Windows Calculator to convert the binary representation of the fol- lowing IP addresses to decimal IP addresses. Binary Decimal 11001010.01000101.01001111.00110101 10001001.00001101.10101010.11111001 11000111.01011111.01000000.10000001 11000011.11011101.11101111.00000101 00000111.11100010.00100000.11111101 10000001.00100101.00001111.10110001 10000011.01000100.00100000.00010110 11. Use Windows Calculator to convert the following decimal IP addresses to a binary representation of IP addresses. Decimal Binary 192.178.44.121 204.18.1.179 10.2.2.76 www.syngress.com 176 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure Continued 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 176 Decimal Binary 141.22.94.107 55.87.191.11 187.34.59.199 99.107.253.224 You might begin to notice patterns with binary numbers.The values of each place- holder are similar to the decimal format, except that decimal is base 10.The first digit in a decimal number is 10 0 , or 1; the second is 10 1 , or 10; the third is 10 3 , or 100; and so on. 111 in decimal is equal to 100 + 10 + 1. In binary representation, each placeholder is base 2, so the first digit in a binary number is 2 0 , or 1; the second is 2 1 , or 2; the third is 2 2 , or 4; and so on.Thus, 111 in binary is equal to 4 + 2 + 1, or 7.Table 3.6 shows a quick summary of one octet in binary. Table 3.6 Binary Notation 128 6432168421 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0 T EST DAY TIP Binary math got you down? Never fear, the standard Windows Calculator will be available for you to use during the exam. It is a good idea to be proficient with the use of the Calculator program in scientific mode, so that you don’t have any doubts during the exam. Be very careful to count your digits in binary results. There are no leading zeros, so 1111111 is actually 011111111, 111111 is actually 00111111, and so on. Despite the convenience of using the Calculator program, you should still understand how to convert binary to decimal manually. Subnetting Networks Subnetting networks is necessary to efficiently manage network resources and control traffic on your network.When your network has grown beyond the capacity of your current infrastructure, you must change your configurations to support those changes. It is relatively simple to identify limitations that are obvious, such as the number of networks and hosts. You can determine the number of networks by counting the number of physical loca- tions that will need a router to connect them to other locations, such as another building or another floor in the same building.You can estimate the number of hosts needed per net- www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 177 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 177 work by counting all the IP-based resources in each physical location, including printers, desktops, servers, and other routers. Once you have that information, you can decide which class of network to use and how to break down that network into logical subnets that will be used to implement each physical or logical location.To summarize, there are three steps to subnetting: 1. Identify the number of hosts. 2. Identify the number of networks. 3. Use an assigned IP network ID or choose a private IP address, and then deter- mine how to subnet your network. As an example, suppose that we have 55 employees in one location, with 12 IP-based network printers, 6 servers, and 1 Internet refrigerator that orders the groceries in the break area when the stock is depleted. Our IP address block assignment provided by our Internet Service Provider (ISP) is 204.74.9.0/24. All the employees are currently located in one large, central area on the same floor. Since we have no physical boundaries to overcome, we use the default subnet mask.This would provide us with one network and 8 bits in the host portion of our address.The 8 bits give us 256 hosts, but the first host is 0, which refers to our network, and the last host is the broadcast address for the network, 255. Remember the formula is 2 n – 2, where n is the number of bits available for host IDs. So, 2 8 – 2 = 256 – 2 = 254 hosts per network. Since we have 74 hosts and one router, that is a total of 75 host IDs.We have plenty of room for growth, and the scheme is simple. The first address on our network starts at 204.74.9.1 (remember 0 is “this network”) and continues to 204.74.9.254 with a subnet mask of 255.255.255.0.Table 3.7 shows an example of the network portion of our address, 204.74.9, and the host portion in the last octet, from 1 to 254. Table 3.7 Breakdown of the Mask for IP Addresses Using a Standard Subnet Mask Source IP Address 204.74.9.21 Destination IP Address 204.74.9.209 Subnet Mask 255.255.255.0 Subnet Mask 255.255.255.0 | —— Network ID —— |. |— Host —| |——— Network ID ——|. |— Host —| 11001100.01001010.00001001.00010000 11001100.01001010.00001001.11010001 11111111.11111111.11111111.00000000 11111111.11111111.11111111.00000000 11001100.01001010.00001001.00000000 11001100.01001010.00001001.00000000 Notice how the results of the subnet mask are equal? Of course, this is a simple example, and we can see just by the address and subnet mask that they are both on the same network. Now we move into the new building where everyone gets his or her very own office. The office has three stories, so we need to break up our simple network into three seg- ments to route between floors.We must use the same IP address block provided. One www.syngress.com 178 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 178 option is to borrow bits from the host IDs and create more subnetworks.The number of subnets is determined by the value of the bits that we borrow from the host IDs. In the example in Table 3.8, we have used 2 bits, shown in bold.The last octet of the subnet mask is now 11000000, or 192.The number of hosts per network is 2 6 – 2, or 62.That should be more than sufficient, so our limitation is the number of networks. Table 3.8 Breakdown of the Mask for IP Addresses Using a Custom Subnet Mask Source IP Address 204.74.9.21 Destination IP Address 204.74.9.209 Subnet Mask 255.255.255.192 Subnet Mask 255.255.255.192 |———— Network ID ———|. |—Host —| |———— Network ID ———|. |—Host —| 11001100.01001010.00001001.00010000 11001100.01001010.00001001.11010001 11111111.11111111.11111111 .11000000 11111111.11111111.11111111.11000000 11001100.01001010.00001001.00000000 11001100.01001010.00001001.11000000 To determine the number of networks we have, we take the bits 11 and use the for- mula 2 n – 2 2 , which is 4, so we can have up to four networks.We can create a list of the networks, convert them to decimal, and get the hosts for each network, as shown in Table 3.9. Remember that the first and last hosts for each network are not assignable. Table 3.9 Determining the Address Blocks Subnet Range Hosts 1 00000001 to 00111110 204.74.9.1 to 204.74.9.62 (204.74.9.0/26) 2 01000001 to 01111110 204.74.9.65 to 204.74.9.126 (204.74.9.64/26) 3 10000001 to 10111110 204.74.9.129 to 204.74.9.190 (204.74.9.128/26) 4 11000001 to 11111110 204.74.9.193 to 204.74.9.254 (204.74.9.192/26) Each network has 62 hosts, and there are 4 networks, so we still have 248 hosts to grow into. We could expand this example by adding satellite offices.Without redesigning the entire subnet, we could use one of the networks that was not used in the example and subnet it further.This is called variable-length subnetting. One of the networks would be broken down into two smaller networks with 30 hosts by borrowing another bit.The net- works would have the notation 204.74.9.0/27 and 204.74.9.33/27.The hosts for 204.74.9.0/27 are 204.74.9.1 to 204.74.9.30, and the hosts for 204.74.9.33/27 are 204.74.9.34 to 204.74.9.63. www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 179 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 179 TEST DAY TIP If you want to use the first and last networks in this scenario, you must use Classless Inter-Domain Routing (CIDR) notation and use routing services that sup- port CIDR. In traditional subnetting, the first network ID is all zeros, so it is “this network,” and the last network ID is all ones, which signifies the broadcast for that network. Classless Inter-Domain Routing (CIDR) You should see now that there are limits to the size of the network you can implement using classful IP address assignment. It has become necessary to provide more options to create larger segments to reduce the size of routing tables and overcome the depleted public IP address pool.The solution is known as Classless Inter-Domain Routing (CIDR). CIDR uses a binary format to provide the definition of network addresses. Use the matrix in Table 3.10 to quickly identify routing and subnet information based on your requirements for the number of hosts and networks.The column of binary masks should help you calculate the networks for each subnet, and the table shows how the classful addressing scheme relates to the CIDR notation. Table 3.10 Quick Matrix for Determining Routing and Subnet Information Required Hosts per Networks CIDR Binary Mask Subnet (2 n –2) Subnet Mask 256 Class B /8 11111111.00000000.00000000.00000000 16,777,212 255.0.0.0 128 Class B /9 11111111.10000000.00000000.00000000 8,388,606 255.128.0.0 64 Class B /10 11111111.11000000.00000000.00000000 4,194,302 255.192.0.0 32 Class B /11 11111111.11100000.00000000.00000000 2,097,150 255.224.0.0 16 Class B /12 11111111.11110000.00000000.00000000 1,048,574 255.240.0.0 8 Class B /13 11111111.11111000.00000000.00000000 524,286 255.248.0.0 4 Class B /14 11111111.11111100.00000000.00000000 262,142 255.252.0.0 2 Class B /15 11111111.11111110.00000000.00000000 131,070 255.254.0.0 1 Class B /16 11111111.11111111.00000000.00000000 65,534 255.255.0.0 256 Class C /16 11111111.11111111.00000000.00000000 65,534 255.255.0.0 128 Class C /17 11111111.11111111.10000000.00000000 32,766 255.255.128.0 www.syngress.com 180 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure Continued 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 180 Table 3.10 Quick Matrix for Determining Routing and Subnet Information Required Hosts per Networks CIDR Binary Mask Subnet (2 n –2) Subnet Mask 64 Class C /18 11111111.11111111.11000000.00000000 16,382 255.255.192.0 32 Class C /19 11111111.11111111.11100000.00000000 8190 255.255.224.0 16 Class C /20 11111111.11111111.11110000.00000000 4094 255.255.240.0 8 Class C /21 11111111.11111111.11111000.00000000 2046 255.255.248.0 4 Class C /22 11111111.11111111.11111100.00000000 1022 255.255.252.0 2 Class C /23 11111111.11111111.11111110.00000000 510 255.255.254.0 1 Class C /24 11111111.11111111.11111111.00000000 254 255.255.255.0 1/2 Class C /25 11111111.11111111.11111111.10000000 126 255.255.255.128 1/4 Class C /26 11111111.11111111.11111111.11000000 62 255.255.255.192 1/8 Class C /27 11111111.11111111.11111111.11100000 30 255.255.255.224 Troubleshooting IP Addressing The flexibility of TCP/IP also contributes to the complexity of troubleshooting addresses and connections.There are several tools that can help isolate and identify issues with addressing, but it is also imperative that you understand IP addressing rules and subnetting. The ipconfig, ping, and tracert commands are the most useful tools for identifying addressing problems with client configurations and connections to other hosts on the Internet. Client Configuration Issues Some of the issues that occur with manual configuration of IP addresses include duplicate addresses, invalid subnet masks, invalid default gateways, and invalid or missing host name resolution settings (such as DNS and WINS).To help identify the problem, start by typing ipconfig /all at a command prompt.Verify the information that is output by the com- mand is correct, and then continue by using ping to help isolate the problem. 1. Ping the loopback address (127.0.0.1) to verify that the TCP/IP protocol stack is configured correctly on the local computer. 2. Ping the external IP address of the local computer to ensure the host is on the network and using a valid IP address; that is, there are no address conflicts. 3. Ping the IP address of the default gateway to verify that the default gateway is accessible and your local network configuration contains the correct subnet mask. 4. Ping the IP address of a remote host to verify that you can transmit data over the default gateway. www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 181 EXAM 70-293 OBJECTIVE 2.6 EXAM 70-293 OBJECTIVE 2.6.1 255_70_293_ch03.qxd 9/10/03 11:56 AM Page 181 [...]... help manage network traffic www.syngress.com 1 93 255_70_2 93_ ch 03. qxd 194 9/10/ 03 11:56 AM Page 194 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure For a DHCP server, the two major factors that affect performance are the amount of physical random access memory (RAM) and the speed of the disk input/output (I/O).You should always provide the largest amount of RAM possible and. .. allows you to view more than one log file at the same time, so that you can compare baseline logs with the current data.The Performance Logs and Alerts service can gather data and store it in a Microsoft SQL Server database that can be viewed by System Monitor.You can also save portions of log files or SQL Server data to a new file This can help save space, simplify comparisons of data, and reduce analysis... utilities and software that uses IPv6, and how to configure and troubleshoot IPv6 using netsh, ipsec6, ping, and tracert commands.We also looked at the 6to4 router and hosts and how they can assist you in making the transition from IPv4 to IPv6 by encapsulation of IPv6 data in IPv4 packets Finally, we examined the tools that are included in Windows Server 20 03 to help you monitor, maintain, and plan your network. .. client C Install TCP/IP on the Windows 95 client D Ensure the server has a valid IP address and implement a DHCP server on the Windows Server 20 03 machine with a valid scope Planning an IP Addressing Strategy 3 You are implementing a test lab that contains three Windows Server 20 03 machines, twenty Windows XP Professional machines, and two IP-based printers.You have been given the network address of... network infrastructure Using those tools, you can identify areas for performance tuning and improving resource availability to minimize network bandwidth utilization and improve network performance Exam Objectives Fast Track Understanding Windows 20 03 Server Network Protocols Windows Server 20 03 supports multiple protocols at the same time using NDIS, allowing better integration and flexibility for network. .. send administrative alerts when specified conditions are met, and even launch an application to allow you to correct the situation or send an e-mail or a page to an administrator.You can save the logs to different file formats to allow you to analyze them in other applications or tools www.syngress.com 255_70_2 93_ ch 03. qxd 9/10/ 03 11:56 AM Page 197 Planning, Implementing, and Maintaining the TCP/IP Infrastructure. .. snap-in tool that allows you to use counters to monitor the performance of hardware, applications, and operating system components on Windows Server 20 03 machines A counter is basically a hook into a driver or application component that allows System Monitor to gather statistics System Monitor can capture these statistics and display them in a graph, as shown in Figure 3. 20, or in a report It can also... tools can be used to create baselines, identify the peak network usage areas, and identify the traffic sources www.syngress.com 255_70_2 93_ ch 03. qxd 9/10/ 03 11:56 AM Page 195 Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 You will also need to monitor network traffic and analyze the usage.You might be able to identify illicit network access from external sites, find Trojan horse...255_70_2 93_ ch 03. qxd 182 9/10/ 03 11:56 AM Page 182 Chapter 3 • Planning, Implementing, and Maintaining the TCP/IP Infrastructure If you are not able to get traffic through to a site, but you are making it through the default gateway, you should use tracert to identify the break in the route to the destination EXAM 70-2 93 OBJECTIVE 2.6.2 DHCP Issues DHCP is an easy way to manage IP addressing schemes for larger... (discussed later in the “Netsh Commands” section) 1 Open Network Connections and double-click the Local Area Network icon You will see the Local Area Connection Status dialog box, as shown in Figure 3. 11 www.syngress.com 255_70_2 93_ ch 03. qxd 9/10/ 03 11:56 AM Page 185 Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 Figure 3. 11 Local Area Connection Status 2 Click Properties 3 In . Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 1 73 EXAM 70-2 93 OBJECTIVE 2.1 .3 255_70_2 93_ ch 03. qxd 9/10/ 03 11:56 AM Page 1 73 The default mask for each class defines the number of networks. that you can transmit data over the default gateway. www.syngress.com Planning, Implementing, and Maintaining the TCP/IP Infrastructure • Chapter 3 181 EXAM 70-2 93 OBJECTIVE 2.6 EXAM 70-2 93 OBJECTIVE 2.6.1 255_70_2 93_ ch 03. qxd. Addressing” section later in this chapter. Each class also has a default subnet mask. Table 3. 3 IP Address Classes and Their Ranges Class Range of Values Default Mask Networks Hosts Binary A 0 to 126 255.0.0.0