Subnetting
Subnetting[edit | edit source]
Subnetting divides an IP network into smaller logical sections called subnets. This structuring improves efficiency, isolates traffic, and defines boundaries between systems and functions.
A deep understanding of subnetting reveals how internal environments are organized, and how access and visibility are controlled across segments.
What Subnetting Enables[edit | edit source]
Subnetting assigns defined IP ranges to roles, departments, or zones. It introduces:
- Predictable address allocation
- Containment of broadcast traffic
- Segmentation between trust levels
- Flexible internal routing logic
Components of a Subnet[edit | edit source]
A subnet is a defined range of IP addresses divided into roles:
- The network address identifies the subnet itself.
- A host address is assigned to devices within the subnet.
- The default gateway forwards traffic beyond the subnet.
| Address Type | Role | Example |
|---|---|---|
| Network Address | Identifies the subnet’s starting point | 10.20.40.0 |
| Host Address | Assigned to individual systems | 10.20.40.17 |
| Default Gateway | Sends traffic to external destinations | 10.20.40.254 |
IP Addresses and Subnet Masks[edit | edit source]
An IPv4 address consists of 32 bits. A subnet mask determines how many bits define the network portion and how many are reserved for hosts.
Examples of subnet divisions:
- `/23` → 255.255.254.0 → 510 usable hosts
- `/26` → 255.255.255.192 → 62 usable hosts
- `/30` → 255.255.255.252 → 2 usable hosts
Smaller subnets reduce broadcast impact and expose fewer devices to lateral access.
Each octet in a subnet mask ranges from 0 to 255, depending on how many bits are allocated to the network portion.
Operational Relevance[edit | edit source]
Subnets reveal the boundaries of where one can move, what is reachable, and how systems relate to each other. Recognizing subnet layout supports:
- Identifying target clusters
- Locating edge devices and chokepoints
- Planning internal traversal across routing paths
- Matching IP observations to physical or functional layout
Example Layout[edit | edit source]
A segmented internal network might include:
| Subnet | Function | Range |
|---|---|---|
| 10.10.0.0/24 | Core servers and directory services | 10.10.0.1 – 10.10.0.254 |
| 10.10.1.0/25 | General employee workstations | 10.10.1.1 – 10.10.1.126 |
| 10.10.2.128/26 | Printers and embedded devices | 10.10.2.129 – 10.10.2.190 |
| 10.10.3.0/28 | External-facing DMZ zone | 10.10.3.1 – 10.10.3.14 |
Each of these zones may route differently, log independently, or apply unique firewall rules.
Strategic Benefits[edit | edit source]
- Minimized exposure – Only devices within the same subnet share direct access
- Tactical segmentation – Movement between zones requires deliberate routing
- Logical clarity – IP ranges reflect organizational structure