What is a Broadcast Address?
The broadcast address is the last address in a subnet, used to send data to all hosts on the network simultaneously. When a device sends a packet to the broadcast address, every device on that subnet receives and processes it. This is essential for protocols like ARP, DHCP, and network discovery services.
For example, in the network 192.168.1.0/24, the broadcast address is 192.168.1.255. Sending a packet to this address reaches all 254 hosts (192.168.1.1 through 192.168.1.254) at once. Like the network address, the broadcast address is reserved and cannot be assigned to any host device. For complete subnet calculations, use our subnet calculator.
Key Point
In binary, the broadcast address has all host bits set to 1. For a /24 network, that's the last 8 bits all being 1 (11111111 = 255), resulting in .255 in the last octet.
How Broadcast Address is Calculated
The broadcast address is calculated by performing a bitwise OR between the network address and the wildcard mask (inverse of subnet mask):
Calculation Example
Network: 192.168.1.0
Wildcard: 0.0.0.255
Binary OR:
Network: 11000000.10101000.00000001.00000000
Wildcard: 00000000.00000000.00000000.11111111
─────────────────────────────────────
OR: 11000000.10101000.00000001.11111111
Broadcast: 192.168.1.255
Common Uses of Broadcast
ARP (Address Resolution Protocol)
When a device needs to find the MAC address for an IP, it sends an ARP request to the broadcast address. All hosts receive the request, but only the one with the matching IP responds.
DHCP Discovery
When a device boots up without an IP address, it broadcasts a DHCP discover message to find available DHCP servers on the network.
Network Discovery
Many services use broadcast to announce their presence or discover other devices, including NetBIOS, mDNS, and various IoT protocols.
Broadcast vs Network Address
| Aspect | Network Address | Broadcast Address |
|---|---|---|
| Position | First in subnet | Last in subnet |
| Host bits | All zeros | All ones |
| Example (/24) | 192.168.1.0 | 192.168.1.255 |
| Purpose | Identifies network | Reaches all hosts |
| Assignable | No | No |
To calculate network addresses, use our network address calculator. For the complete picture including both addresses, see the CIDR calculator.
Directed vs Limited Broadcast
Directed Broadcast
A directed broadcast targets a specific subnet's broadcast address (e.g., 192.168.1.255). It can potentially be routed to reach that subnet from another network, though most routers disable this for security.
Limited Broadcast (255.255.255.255)
The address 255.255.255.255 is the limited broadcast address. It reaches all hosts on the local network segment only and is never routed by routers.
For more details on IP address types, use our IP address validator.