As shown in the figure, which of the following routes can be matched by this prefix list? (Multiple choice) [HUAWEI]ip ip-prefix test index 10 permit 20.0.0.0 16 greater-equal 24 less-equal 28

Question

Options

• A20.0.1.0/24
• B20.0.0.0/29
• C20.0.0.0/23
• D20.0.0.0/28

• A
  81% (34)
• C
  19% (8)

Explanation

Important note: There appears to be an error in the provided answer key. Based on the command as written, only A and D are correct - not B. Here is the accurate explanation:

The prefix list permit 20.0.0.0 16 greater-equal 24 less-equal 28 matches any route whose network address falls within the 20.0.0.0/16 supernet and whose prefix length is between /24 and /28 inclusive. Options A (20.0.1.0/24) and D (20.0.0.0/28) both satisfy both conditions - their first 16 bits match 20.0, and their masks (/24 and /28) sit exactly within the allowed range.

Why B is wrong: 20.0.0.0/29 has a prefix length of 29, which exceeds the less-equal 28 ceiling - it is too specific and falls outside the permitted range.

Why C is wrong: 20.0.0.0/23 has a prefix length of 23, which is below the greater-equal 24 floor - it is too broad and also fails.

Memory tip: Think of the base prefix (20.0.0.0/16) as the "address filter" and greater-equal/less-equal as the "mask length window" - a route must pass both tests simultaneously. The phrase "ge means at least, le means at most" keeps the bounds straight under exam pressure.

Verdict: The answer key listing B as correct appears to be a misprint. Confirm with your source - the command less-equal 28 definitively excludes /29.

No community discussion yet for this question.