Quiz Entry - updated: 2026.07.14
How do you subnet on an octet boundary (/8, /16, /24)?
Subnetting on an octet boundary means the mask ends exactly at a dot — /8, /16, or /24 — so whole octets are network and whole octets are host, making the math easy to do mentally.
Subnetting on Octet Boundaries:
The simplest form of subnetting - dividing at the 8-bit boundaries.
Standard Octet-Boundary Masks:
| Prefix | Subnet Mask | Network Octets | Host Octets |
|---|---|---|---|
| /8 | 255.0.0.0 | 1st | 2nd, 3rd, 4th |
| /16 | 255.255.0.0 | 1st, 2nd | 3rd, 4th |
| /24 | 255.255.255.0 | 1st, 2nd, 3rd | 4th |
Example: 172.16.0.0/16 subnetted to /24
- Original: 1 network with 65,534 hosts
- After /24 subnetting: 256 subnets with 254 hosts each
Resulting subnets:
- 172.16.0.0/24
- 172.16.1.0/24
- 172.16.2.0/24
- ... through ...
- 172.16.255.0/24
Context: Octet-boundary subnetting is easy to calculate mentally but may not efficiently use address space.
Go deeper:
Subnetting is simple — Sunny Classroom (YouTube) — a clear visual walk-through of how the mask divides the address.
Subnet (Wikipedia) — the underlying network/host division that octet boundaries land on.