ITPEC FE Morning October 2022 Question 32
ITPEC FE Morning October 2022 — Question 32 of 80
Subnet Mask from CIDR Notation — convert /27 to dotted-decimal subnet mask.
/27 means 27 bits are set to 1 in the mask.
- •First 24 bits fill 3 full octets:
255.255.255.___ - •Remaining 3 bits in the 4th octet:
11100000=224 - •Result:
255.255.255.224
Quick reference — 4th octet values by prefix length:
- /25 → 128, /26 → 192, /27 → 224, /28 → 240
- /29 → 248, /30 → 252, /31 → 254, /32 → 255
Why not others:
- (a) 255.255.255.192 — corresponds to /26 (2 bits in last octet)
- (c) 255.255.255.248 — corresponds to /29 (5 bits in last octet)
- (d) 255.255.255.252 — corresponds to /30 (6 bits in last octet)
Key rule: Subtract 24 from the prefix length to get the number of 1 bits in the last octet, then compute 256 − 2^(8 − bits).
AI-generated — may contain errors
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