ITPEC FE Morning April 2018 Question 33
ITPEC FE Morning April 2018 — Question 33 of 80
Subnet membership check — determine if two IPs share the same subnet.
Subnet mask 255.255.255.240 = /28 → last octet = 240 = 11110000.
- •Host bits: 4 → block size =
2⁴ = 16 - •Subnet boundaries (last octet):
0, 16, 32, 48, 64...
Quick method: integer part of (last_octet ÷ block_size) — if equal, same subnet.
Check each pair:
- (a) .14 → 14 ÷ 16 = 0, .17 → 17 ÷ 16 = 1 → different subnets
- (b) .17 → 17 ÷ 16 = 1, .29 → 29 ÷ 16 = 1 → same subnet ✅
- (c) .29 → 29 ÷ 16 = 1, .33 → 33 ÷ 16 = 2 → different subnets
- (d) .33 → 33 ÷ 16 = 2, .49 → 49 ÷ 16 = 3 → different subnets
Answer: (b)
Key rule: Convert mask to block size (256 - mask_octet), then divide host octets by block size. Equal quotients = same subnet.
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