The broadcast address is simply the last address in a subnet — every host bit set to 1. A packet sent there reaches every host in that subnet. Here are three ways to find it; pick the one that clicks.

Method 1 — all host bits to 1

Write the address in binary, keep the network bits, and set every host bit to 1. The result is the broadcast. Slow but it always works and shows you why.

Method 2 — the block-size shortcut (fastest)

The block size is 256 − (the "interesting" octet of the mask). Subnets begin at multiples of that block size. The broadcast is the next network minus one.

Example — 192.168.1.0/26:

/26 mask = 255.255.255.192
Block size = 256 - 192 = 64
Subnets:   .0   .64   .128   .192
Subnet .0  ->  network .0,  broadcast .63   (next net .64 minus 1)
Subnet .64 ->  network .64, broadcast .127

So a host like 192.168.1.100/26 lives in the .64 subnet, and its broadcast is 192.168.1.127.

Method 3 — network OR inverse mask

Take the network address and add the wildcard (inverse) mask. For /26, the wildcard is 0.0.0.63, so network .64 + 63 = broadcast .127. Same answer, pure arithmetic.

Sanity checks

  • Broadcast is always one less than the next subnet's network address.
  • The last usable host is always broadcast − 1.
  • A /31 has no broadcast (point-to-point); a /32 is a single host.