Networking
10 seconds
10-second mask challenge: /27
Ten seconds. Go. What block size does a /27 make?
Quick check · tap an answer to continue
Lesson notes
Key points
- Subtract the interesting octet from 256: 256 − 224 = 32.
- So subnets start at .0, .32, .64, .96 and so on.
Takeaway: 256 − mask octet gives the subnet block size instantly.
Quick check: Mask 255.255.255.224 (/27): what is the block size, the jump between subnets?
- 16
- 32
- 64
Block size = 256 minus the last non-255 octet of the mask.
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