CompTIA Network+ IP Addressing and Subnetting Questions and Answers

Question 1

A network technician is configuring a workstation and observes its IP address is 169.254.100.51. The user reports they cannot access the internet or the company's file server. What is the MOST likely cause of this issue?

Accepted Answer

The workstation failed to obtain an IP address from the DHCP server.

Answer

The IP address 169.254.100.51 is an Automatic Private IP Addressing (APIPA) address. Operating systems assign APIPA addresses when a device is configured for DHCP but cannot contact a DHCP server. This allows for communication on the local subnet but not for routed traffic to other networks or the internet.

Question 2

A network administrator needs to create a subnet that can support up to 25 usable host addresses. Which of the following CIDR notations provides the required number of hosts while minimizing wasted IP addresses?

Accepted Answer

/27

Answer

To find the number of usable hosts, use the formula 2^h - 2, where 'h' is the number of host bits. A /27 prefix leaves 5 host bits (32 - 27 = 5). Calculating 2^5 - 2 gives 30 usable hosts. A /28 (14 hosts) is too small, and a /26 (62 hosts) wastes more addresses.

Question 3

Which of the following IP addresses is a non-routable, private address according to RFC 1918?

Accepted Answer

192.168.20.1

Answer

RFC 1918 defines specific ranges for private IP addressing. The range 192.168.0.0 to 192.168.255.255 is one of these private ranges. The 172.16.0.0/12 range is also private, but 172.32.x.x falls outside of it. The 11.x.x.x address is public, and 169.254.x.x is reserved for APIPA.

Question 4

A network administrator is given the IP address 192.168.50.133 and the subnet mask 255.255.255.240. What is the subnet address for this host?

Accepted Answer

192.168.50.128

Answer

The subnet mask 255.255.255.240 (/28) creates subnets in increments of 16 in the fourth octet (256-240=16). The subnets are .0, .16, .32, etc. The address 192.168.50.133 falls into the subnet that starts at 192.168.50.128 and ends with the broadcast address 192.168.50.143.

Question 5

A subnet mask of 255.255.252.0 is equivalent to which CIDR prefix notation?

Accepted Answer

/22

Answer

CIDR notation represents the number of leading '1's in the subnet mask's binary representation. 255.255.252.0 in binary is 11111111.11111111.11111100.00000000. Counting the number of '1's gives a total of 8 + 8 + 6 = 22. Therefore, the CIDR notation is /22.

CompTIA Practice Test

CompTIA Practice Test

CompTIA Network+ IP Addressing and Subnetting Questions and Answers