Computer Networks — Test 17

Correct Answer: D. D. 30
Explanation: A /27 (255.255.255.224) is 3 bits on and 5 bits off. This provides 8 subnets, each with 30 hosts. Does it matter if this mask is used with a Class A, B, or C network address? Not at all. The number of host bits would never change.

Correct Answer: B. B. 255.255.255.224
Explanation: You need 5 subnets, each with at least 16 hosts. The mask 255.255.255.240 provides 16 subnets with 14 hosts which is less than 15, so this will not work. The mask 255.255.255.224 provides 8 subnets, each with 30 hosts so this may work. The mask 255.255.255.192 provides 4 subnets, each with 60 hosts so this may work. Comparing both the possible masks, 255.255.255.224 provides the best answer.

Correct Answer: D. D. 5
Explanation: A 240 mask is 4 subnet bits and provides 16 subnets, each with 14 hosts. We need more subnets, so let’s add subnet bits. One more subnet bit would be a 248 mask. This provides 5 subnet bits (32 subnets) with 3 host bits (6 hosts per subnet). This is the best answer.

Correct Answer: A. A. 172.16.112.0
Explanation: A /25 mask is 255.255.255.128. Used with a Class B network, the third and fourth octets are used for subnetting with a total of 9 subnet bits, 8 bits in the third octet and 1 bit in the fourth octet. Since there is only 1 bit in the fourth octet, the bit is either off or on-which is a value of 0 or 128. The host in the question is in the 0 subnet, which has a broadcast address of 127 since 128 is the next subnet

Correct Answer: A. A. 6
Explanation: A /29 (255.255.255.248), regardless of the class of address, has only 3 host bits. Six hosts are the maximum number of hosts on this LAN, including the router interface. Out of the 8 addresses possible with the host bits, the first and the last address are for the subnet id and broadcast address respectively.

Correct Answer: C. C. 172.16.64.0
Explanation: A /21 is 255.255.248.0, which means we have a block size of 8 in the third octet, so we just count by 8 until we reach 66. The subnet in this question is 64.0. The next subnet is 72.0, so the broadcast address of the 64 subnet is 71.255.

Correct Answer: B. B. 8 subnets, 8,190 hosts each
Explanation: A CIDR address of /19 is 255.255.224.0. This is a Class B address, so that is only 3 subnet bits, but it provides 13 host bits, or 8 subnets, each with 8,190 hosts.

Correct Answer: C. C. 10110001
Explanation: High – 1, Low – 0.

Correct Answer: A. A. Synchronous optical network
Explanation: SONET stands for synchronous optical network. Frame relay uses SONET to physically transmit data frames over a Frame Relay network as SONET is cheaper and provides better network reliability than other carriers.

Correct Answer: A. A. 51.84 mbps
Explanation: STS-1 level provides the data rate of 51.84 Mbps, STS-3 provides a data rate of 155.52 Mbps, STS-12 provides a data rate of 622.080 Mbps and STS-48 provides a data rate of 2488.320 Mbps.