Every subnet has two special addresses you can't assign to devices. Here's why — and what each one does.
What Is a Network Address?
The network address is the first IP in a subnet. It identifies the subnet as a whole, like calling a building by its street name instead of a unit number.
Subnet: 192.168.1.0/24 Network Address: 192.168.1.0
This address represents the entire subnet in routing tables. When a router needs to send traffic to "the 192.168.1.0 network," it uses this address.
What Is a Broadcast Address?
The broadcast address is the last IP in a subnet. Sending data here reaches EVERY device on the subnet simultaneously.
Subnet: 192.168.1.0/24 Broadcast Address: 192.168.1.255
When a device sends to the broadcast address, all devices on that subnet receive it. This is useful for certain protocols but shouldn't be used for regular communication.
Examples for Different Subnet Sizes
| Subnet | Network Addr | First Usable | Last Usable | Broadcast |
|---|---|---|---|---|
| /24 | 192.168.1.0 | 192.168.1.1 | 192.168.1.254 | 192.168.1.255 |
| /25 | 192.168.1.0 | 192.168.1.1 | 192.168.1.126 | 192.168.1.127 |
| /26 | 192.168.1.64 | 192.168.1.65 | 192.168.1.126 | 192.168.1.127 |
| /27 | 192.168.1.192 | 192.168.1.193 | 192.168.1.222 | 192.168.1.223 |
| /28 | 192.168.1.224 | 192.168.1.225 | 192.168.1.238 | 192.168.1.239 |
How to Calculate Them
Given any IP in a subnet, here's how to find the network and broadcast addresses:
Example: IP 192.168.1.100/26
Step 1: Find the subnet mask /26 = 255.255.255.192 Step 2: Network address (all host bits = 0) 192.168.1.100 AND 255.255.255.192 = 192.168.1.64 Step 3: Broadcast address (all host bits = 1) 192.168.1.64 + 63 = 192.168.1.127 Result: - Network: 192.168.1.64 - Broadcast: 192.168.1.127 - Usable: 192.168.1.65 - 192.168.1.126 (62 hosts)
Why These Addresses Exist
- Network address: Used in routing tables to identify the subnet
- Broadcast address: Used for ARP (finding MAC addresses), DHCP, and certain discovery protocols
Without these special addresses, devices wouldn't have a standard way to find each other on the local network or know which subnet they're part of.
Common Mistake to Avoid
When configuring static IPs, beginners often make this mistake:
WRONG: - Gateway: 192.168.1.0 (that's the network address!) - Device IP: 192.168.1.255 (that's the broadcast!) RIGHT: - Gateway: 192.168.1.1 (or any usable address) - Device IP: 192.168.1.100 (any address between first and last usable)
Use the calculator to always check first and last usable addresses before assigning static IPs!