BeginnerPhone
1 min
What does /24 mean in CIDR?
NetworkingIPv4Subnetting
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Interview Question
In CIDR notation, what does a /24 signify and roughly how many usable IPv4 addresses are in such a subnet?
Key Points to Cover
- /24 means 255.255.255.0 (24-bit network mask)
- 256 total addresses; ~254 usable (excluding network and broadcast)
- 8 bits remaining for host addresses (2^8 = 256)
Evaluation Rubric
States /24 equals 255.255.255.040% weight
Mentions ≈254 usable addresses40% weight
Explains the bit calculation20% weight
Hints
- 💡Think: 32 total bits; 24 for the network portion.
Common Pitfalls to Avoid
- ⚠️Forgetting to subtract the network and broadcast addresses when calculating usable hosts.
- ⚠️Incorrectly converting /24 to the dotted decimal subnet mask (e.g., not knowing 255.255.255.0).
- ⚠️Confusing the number of network bits with the number of host bits.
- ⚠️Not understanding the significance of 2^N (where N is the number of host bits) for calculating total addresses.
- ⚠️Providing a general definition of CIDR without specifically addressing the /24 notation.
Potential Follow-up Questions
- ❓What about /16 or /8?
- ❓How would you subnet a /24 into smaller networks?
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