Among the following options, which routing prefixes satisfy the following IP-Prefix conditions? (Multiple choice) [HUAWEI] ip ip-prefix test index 10 permit 20.0.1.0 16 greater-equal 24 less-equal 28

Question

Options

• A20.0.1.0/24
• B20.0.1.0/23
• C20.0.1.0/26
• D20.0.1.0/28

• A
  74% (39)
• B
  15% (8)
• C
  4% (2)
• D
  8% (4)

Explanation

Option A (20.0.1.0/24) satisfies the ip-prefix rule because the command permit 20.0.1.0 16 greater-equal 24 less-equal 28 matches any prefix whose first 16 bits equal those of 20.0.0.0 (i.e., any 20.0.x.x network) and whose prefix length falls between 24 and 28 inclusive - 20.0.1.0/24 has a length of exactly 24, which is the lower bound of that range.

Option B (20.0.1.0/23) fails the length check: a /23 prefix length is less than the greater-equal 24 minimum, so it is rejected regardless of the network address.

Note on C and D: By standard Huawei ip-prefix matching logic, 20.0.1.0/26 (/26 is between 24–28 ) and 20.0.1.0/28 (/28 equals the upper bound ) also satisfy the stated conditions. If the exam marks only A as correct, either the question contains an error in the answer key, or the original options were different (e.g., /29 or /30 for C/D, which would exceed the less-equal 28 ceiling and correctly fail).

Memory tip: Think of the three-part filter as a funnel - (1) Does the network fall inside the base /16 block? → (2) Is the mask length ≥ ge? → (3) Is the mask length ≤ le? Any prefix that fails any one of the three gates is denied. For B, gate 2 is the failure.

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