4.1 - IP Addressing

Question 1: What is the decimal form of the following binary IP address? 11001110.00111010.10101010.01000011 206.58.170.67 238.90.202.99 205.57.169.66 190.42.154.51 Explanation 206.58.170.67 is the decimal form of this IP address. To convert binary to decimal, remember the following numbers: 128, 64, 32, 16, 8, 4, 2, 1. Each number represents the decimal value for a binary 1 in the corresponding position. For example, 10000000 is equal to 128, and 00010000 is equal to 16. To find the decimal form of a binary number, add up each decimal equivalent for each 1 bit in the address. For example, the equation for the number 11001110 is 128 + 64 + 8 + 4 + 2 = 206. Question 2: Incorrect Match each decimal value on the left with the corresponding hexadecimal value on the right. Not all decimal values have a corresponding hexadecimal value. 11 17 B 11 D  13 F 15 C 12 10 16 Keyboard Instructions

Explanation Hexadecimal is a base-16 numbering system, which means that there are 16 possible characters for each number place. These characters range from 0 to 9, as decimal does. However, hexadecimal uses the letter A to represent the decimal number 10, B to represent 11, and so on, up to F (which represents 15). The easiest way to convert between decimal and hexadecimal is to memorize the corresponding values for each hexadecimal number using the following tables. Hex Value 0 1 2 3 4 5 6 7 8 9 A B C D E F Decimal Value 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Hex Value 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F Decimal Value 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Question 3: Drag each binary subnet mask on the left to its appropriate decimal equivalent on the right. 255.0.0.0 11111111.00000000.00000000.00000000 255.255.255.128 11111111.11111111.11111111.10000000 255.224.0.0  11111111.11100000.00000000.00000000 255.255.0.0 11111111.11111111.00000000.00000000 255.255.255.252  11111111.11111111.11111111.11111100 Keyboard Instructions Explanation To perform subnetting operations, you need to be proficient at converting decimal and binary numbers. When you work with IP addresses, work with each octet separately. The following list shows the decimal value for various binary values with a single 1 bit:  10000000: 128  01000000: 64  00100000: 32  00010000: 16  00001000: 8

16777214 Explanation Given a network address and subnet mask, you can have 2 to the  n  power - 2 (2 hosts per subnet). Begin by converting the subnet mask to a binary number. To find the number of valid hosts,  n = the number of unmasked bits in the mask. In this example, there are 16 unmasked bits. So the number of available hosts is 2 to the 16th power - 2, which equals 65534. Question 6: A host has an address of 100.55.177.99/16. Which of the following is the broadcast address for the subnet? 255.255.255.0 255.255.0.0 100.55.255.255 100.255.255.255 Explanation The broadcast address for the subnet is the last address on the subnet. In this example, the address uses 16 bits in the subnet mask (255.255.0.0), meaning that the first two octets indicate the subnet address (100.55.0.0), and the last two octets are used for host addresses. The last possible address on this subnet is 100.55.255.255. Question 7: Your network has a network address of 172.17.0.0 with a subnet mask of 255.255.255.0. Which of the following are true concerning this network? (Select two.) 172.17.0.1 is reserved for the default gateway. 256 IP addresses can be assigned to host devices. 254 IP addresses can be assigned to host devices. 172.17.0.255 is the network broadcast address. 172.17.255.255 is the network broadcast address. Explanation You can subnet a Class B address to provide additional subnet addresses. (Notice how, by using a custom subnet mask, the Class B address looks like a Class C address.)  Network address: 172.17.0.0

 Subnet mask: 255.255.255.0  Number of subnets: 256  Number of hosts per subnet: 254  Subnet addresses: 172.17.1.0, 172.17.2.0, 172.17.3.0, and so on  Host address ranges: 172.17.1.1 to 172.17.1.254, 172.17.2.1 to 172.17.2.254, 172.17.3.1 to 172.17.3.254, and so on Question 8: Which of the following best describes the purpose of using subnets? Subnets let you connect a private network to the internet. Subnets place each device within its own collision domain. Subnets divide an IP network address into multiple network addresses. Subnets combine multiple IP network addresses into one network address. Explanation Subnets divide an IP network address into multiple network addresses. This allows you to have several smaller networks while using only one network address. With supernetting, multiple smaller subnets are combined into a single larger subnet. With modern switched networks, each switch port represents its own collision domain. Network Address Translation (NAT) allows you to connect a private network to the internet. Question 9:

When you connect a private network to the internet, only the router interface connected to the internet needs a public address. You can then use Network Address Translation (NAT) and assign private addresses to hosts on your private network (including all the routers on the private network). The NAT router translates your private addresses into public addresses. You can even use NAT to place publicly available hosts, such as web servers, on a private network (although these servers are often placed on a special subnet that's connected to the internet and assigned public addresses). With port address translation, incoming messages sent to the publicly available servers are relayed to the private network. Servers that hold confidential data, such as database servers, are normally placed on a private network. Generally, they can only be contacted directly by the necessary devices (such as a web server).