300-320 Question #381: Real Exam Question with Answer & Explanation

The correct answer is C: The size of the contiguous block of addresses. The three-step process to verify that a contiguous block of IP addresses can be summarized into a single supernet/summary route all rely on the block size (number of addresses in the range): Step 1 - Determine the block size: Count the number of addresses in the range. The block

Question

here are 3 steps to confirm whether a range of IP addresses can be summarized. Which of the following is used in each of these 3 steps?

Options

AThe first number in the contiguous block of addresses
BThe last number in the contiguous block of addresses
CThe size of the contiguous block of addresses
DThe subnet mask of the original network address

Explanation

The three-step process to verify that a contiguous block of IP addresses can be summarized into a single supernet/summary route all rely on the block size (number of addresses in the range): Step 1 - Determine the block size: Count the number of addresses in the range. The block size must be a power of 2 (e.g., 4, 8, 16, 32, etc.) to be summarizable. Step 2 - Verify alignment: The first address in the block must be divisible by the block size (i.e., the starting address must fall on a block boundary). Step 3 - Derive the summary mask: The block size directly determines the subnet mask (e.g., block size 16 = /28 = 255.255.255.240). The first address (A) and last address (B) are inputs, but they are not used in all three steps - the block size derived from them is. The original subnet mask (D) is not part of summarization verification. The block size (C) is the central value used throughout all three validation steps.

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