How many usable IP addresses are there in a 20-bit subnet?

A /20 subnet means 32 - 20 = 12 bits are available for host addresses.

Total IPs: 2¹² = 4096

Usable IPs = 4096 - 2 = 4094 (excluding network and broadcast addresses)

Therefore, 4094 usable IP addresses exist in a /20 subnet.

Option breakdown:

A. 2047 → Incorrect, would apply to a /21 subnet (2048 total - 1)

B. 4096 → Incorrect, total IPs, not usable

C. 2048 → Incorrect

D. 2046 → Incorrect

E. 4094 →✔Correct

Extract from MTCNA Course Material – IP Addressing/Subnetting Section:

"Number of usable hosts = 2^host-bits - 2 (network and broadcast). For /20, 2^12 - 2 = 4094."

Extract from Terry Combs Notes – IP Subnet Calculations:

“A /20 gives 4096 IPs total, 4094 usable.”

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