CompTIA Network+ (N10-007) — Question 691

A network administrator has signed up for service with a new ISP. The administrator was given the IP address of 172.17.10.254/30 to use on the external interface of the Internet-facing router. However, the network administrator cannot reach the Internet using that address. Which of the following is the MOST likely explanation?

Answer options

• A. The address provided by the ISP has a mask that is too small to be used and needs a larger mask.
• B. The address provided by the ISP is a private IP address space and is not routable on the Internet.
• C. The address provided by the ISP is the wrong one; they should be using 172.17.10.252/30.
• D. The address provided by the ISP is part of the reserved loopback address space and cannot be used.

Correct answer: B

Explanation

The correct answer is B because the IP address 172.17.10.254/30 is part of the private IP address space, which is not routable on the Internet. Options A and D are incorrect because the subnet mask is appropriate for using a /30 address, and the address is not part of the loopback range. Option C is also incorrect as the address given is valid for private use, not an incorrect assignment.