Networking
Explainer
Reading /24: Subnetting Made Clear
How many usable hosts fit in a /26 network? Most students say 64.
Quick check · tap an answer to continue
Lesson notes
Key points
- An IPv4 address has 32 bits, and the CIDR prefix like /26 counts how many bits identify the network.
- The remaining host bits set the block size, so a /26 leaves six host bits, giving 64 addresses.
- Two addresses are reserved: the network address with all host bits zero and the broadcast with all ones.
- So usable hosts equal two to the host bits minus two, giving 62 for a /26, a classic exam trap.
Definitions
- CIDR prefix
- The number of leading bits in an IPv4 address that form the network portion.
Takeaway: Usable hosts = 2^(32 − prefix) − 2.
Quick check: How many usable hosts are in a /27 network?
- 30
- 32
- 27
CIDR prefixHost bitsReserved addressesUsable hosts
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