TCP/IP Solution - Quiz Explanation

The correct answers are indicated below, along with brief explanations of why each answer is correct.

1. Choose an appropriate subnet mask for hosts in this design.
Please select the best answer.
 A./16
 B./19
 C./21
 D./24
  The correct answer is D. A /24 subnet mask leaves 8 host bits. That yields 28 − 2 = 254 usable host addresses per subnet, which is appropriate when the design requires fewer than ~254 hosts per subnet (plus modest growth).

Why the others are incorrect:
  • /16 leaves 16 host bits: 216 − 2 = 65,534 hosts per subnet (far larger than needed).
  • /19 leaves 13 host bits: 213 − 2 = 8,190 hosts per subnet.
  • /21 leaves 11 host bits: 211 − 2 = 2,046 hosts per subnet.
Note: 7 host bits would yield 27 − 2 = 126 hosts per subnet, which may be too small for many designs.

2. What is the total number of required private host IP addresses?
Please select the best answer.
 A.7 private IP addresses
 B.1,204 private IP addresses
 C.2,903 private IP addresses
 D.4,032 private IP addresses
  The correct answer is C. 2,903 is the total number of required private host IP addresses in the design (excluding additional addresses needed for router interfaces). This value is obtained by summing the host requirements across locations.

3. What is the minimum number of required public IP addresses?
Please select the best answer.
 A.1 public IP address
 B.2,903 public IP addresses
 C.2 public IP addresses
 D.4,032 public IP addresses
  The correct answer is A. Only the Internet-facing interface requires a public IP address. Internal hosts can use private IP addressing and still access Internet resources through NAT/PAT (or a proxy server) at the edge. The other answers are incorrect because they assume public IPs are required for every internal host.

4. At maximum, how many hosts per subnet does the subnet mask in the design provide?
Please select the best answer.
 A.254 hosts per subnet
 B.1,022 hosts per subnet
 C.6,398 hosts per subnet
 D.65,534 hosts per subnet
  The correct answer is A. A /24 subnet mask leaves 8 host bits, which yields 28 − 2 = 254 usable host addresses per subnet. Therefore, the maximum number of hosts per subnet is 254.
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