A network address and a broadcast address are two special IP addresses that exist within every IPv4 subnet, and they sit at opposite ends of that subnet's address range with opposite purposes.
Network address
- This is the first address in a subnet's range.
- It identifies the network (or subnet) itself as a whole, rather than any individual device on it.
- It's formed by taking the IP address and setting all the "host" bits (the portion not covered by the subnet mask) to 0.
- It's used by routers and networking equipment for routing purposes — to identify which subnet a packet belongs to — and cannot be assigned to an individual host/device.
Broadcast address
- This is the last address in a subnet's range.
- It's formed by setting all the host bits to 1.
- A packet sent to this address is delivered to every device on that local subnet simultaneously — it's used for one-to-all communication within the subnet (e.g., ARP requests, DHCP discovery messages).
- Like the network address, it cannot be assigned to an individual host.
Example For the subnet 192.168.1.0/24 (subnet mask 255.255.255.0):
- Network address: 192.168.1.0 (all host bits = 0)
- Broadcast address: 192.168.1.255 (all host bits = 1)
- Usable host addresses: 192.168.1.1 through 192.168.1.254
Key distinction: the network address represents the subnet's identity as a whole, while the broadcast address is a destination that reaches all hosts on that subnet at once. Both are reserved and excluded from the pool of addresses that can be assigned to individual devices, which is why a /24 subnet with 256 total addresses only provides 254 usable host addresses.
Note: IPv6 doesn't use broadcast addresses at all — it relies on multicast instead — so this concept is specific to IPv4 networking.