CISCO CCNA I - Module 11 - IPv4 Addressing (Test Notes)

What subnet mask is represented by the slash notation /20? a. 255.255.255.192 b. 255.255.224.0 c. 255.255.255.0 d. 255.255.255.248 e. 255.255.240.0

255.255.240.0 Explanation: The slash notation /20 represents a subnet mask with 20 1s. This would translate to: 11111111.11111111.11110000.0000, which in turn would convert into 255.255.240.0.

A network administrator is variably subnetting a network. The smallest subnet has a mask of 255.255.255.224. How many usable host addresses will this subnet provide?​ a. 6 b. 2 c. 14 d. 62 e. 30

30 Explanation: 255.255.255.224 = /27 (2^n - 2 = # of usable hosts), n = 32 - the mask. (/27 in this case). So, (2^5 - 2 = 30). The subnet mask 255.255.255.224 is equivalent to the /27 prefix. This leaves 5 bits for hosts, providing a total of 30 usable IP addresses (2^5 = 32 - 2 = 30).

How many usable IP addresses are available on the 192.168.1.0/27 network? a. 32 b. 30 c. 16 d. 254 e. 62 f. 256

30 Explanation: A /27 mask is the same as 255.255.255.224. This leaves 5 host bits. With 5 host bits, 32 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address. Thus, 30 addresses can then be used to assign to network devices.

A network administrator subnets the 192.168.10.0/24 network into subnets with /26 masks. How many equal-sized subnets are created? a. 1 b. 8 c. 2 d. 4 e. 16 f. 64

4 Explanation: The normal mask for 192.168.10.0 is /24. A /26 mask indicates 2 bits have been borrowed for subnetting. With 2 bits, four subnets of equal size could be created.​

Which two parts are components of an IPv4 address? (Choose two.) a. logical portion b. network portion c. physical portion d. broadcast portion e. host portion f. subnet portion

network portion & host portion (b & e) Explanation: An IPv4 address is divided into two parts: a network portion - to identify the specific network on which a host resides, and a host portion - to identify specific hosts on a network. A subnet mask is used to identify the length of each portion.

What is the prefix length notation for the subnet mask 255.255.255.224? a. /27 b. /28 c. /26 d. /25

/27 Explanation: The binary format for 255.255.255.224 is 11111111.11111111.11111111.11100000. The prefix length is the number of consecutive 1s in the subnet mask. Therefore, the prefix length is /27.

If a network device has a mask of /28, how many IP addresses are available for hosts on this network? a. 16 b. 254 c. 32 d. 14 e. 62 f. 256

14 Explanation: (2^n - 2 = # of usable hosts), n = 32 - the mask. (/28 in this case). So, (2^4 - 2 = 14). A /28 mask is the same as 255.255.255.240. This leaves 4 host bits. With 4 host bits, 16 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address. 14 addresses can then be used to assign to network devices.

Which subnet mask would be used if exactly 4 host bits are available? a. 255.255.255.224 b. 255.255.255.128 c. 255.255.255.248 d. 255.255.255.240

255.255.255.240 Explanation: The subnet mask of 255.255.255.224 has 5 host bits. The mask of 255.255.255.128 results in 7 host bits. The mask of 255.255.255.240 has 4 host bits. Finally, 255.255.255.248 represents 3 host bits.

Which subnet mask would be used if 5 host bits are available? a. 255.255.255.224​ b. 255.255.255.0 c. 255.255.255.240 d. 255.255.255.128

255.255.255.224 Explanation: The subnet mask of 255.255.255.0 has 8 host bits. The mask of 255.255.255.128 results in 7 host bits. The mask of 255.255.255.224 has 5 host bits. Finally, 255.255.255.240 represents 4 host bits.

If a network device has a mask of /26, how many IP addresses are available for hosts on this network? a. 14 b. 64 c. 30 d. 32 e. 62 f. 16

62 Explanation: (2^n - 2 = # of usable hosts), n = 32 - the mask. (/26 in this case). So, (2^6 - 2 = 62). A /26 mask is the same as 255.255.255.192. This leaves 6 host bits. With 6 host bits, 64 IP addresses are possible, but one address represents the subnet number and one address represents the broadcast address. Thus 62 addresses can then be assigned to network hosts.

How many valid host addresses are available on an IPv4 subnet that is configured with a /26 mask? a. 254 b. 64 c. 192 d. 62 e. 190

62 Explanation: When a /26 mask is used, 6 bits are used as host bits. With 6 bits, 64 addresses are possible, but one address is for the subnet number and one address is for a broadcast. This leaves 62 addresses that can be assigned to network devices.

Which statement is true about variable-length subnet masking? a. Subnets may only be subnetted one additional time. b. The size of each subnet may be different, depending on requirements. c. Bits are returned, rather than borrowed, to create additional subnets. d. Each subnet is the same size.

The size of each subnet may be different, depending on requirements. Explanation: In variable-length subnet masking, bits are borrowed to create subnets. Additional bits may be borrowed to create additional subnets within the original subnets. This may continue until there are no bits available to borrow.

What does the IP address 172.17.4.250/24 represent? a. broadcast address b. multicast address c. host address d. network address

host address Explanation: The /24 shows that the network address is 172.17.4.0. The broadcast address for this network would be 172.17.4.255. Usable host addresses for this network are 172.17.4.1 through 172.17.4.254.

What is the purpose of the subnet mask in conjunction with an IP address? a. to uniquely identify a host on a network b. to mask the IP address to outsiders c. to determine the subnet to which the host belongs d. to identify whether the address is public or private

to determine the subnet to which the host belongs Explanation: With the IPv4 address, a subnet mask is also necessary. A subnet mask is a special type of IPv4 address that coupled with the IP address determines the subnet of which the device is a member. ​

Why does a Layer 3 device perform the ANDing process on a destination IP address and subnet mask? a. to identify the network address of the destination network b. to identify the broadcast address of the destination network c. to identify the host address of the destination host d. to identify faulty frames

to identify the network address of the destination network Explanation: ANDing allows us to identify the network address from the IP address and the network mask.