- IP Broadcast Address
- The IP broadcast address is the last address in a range of IP addresses and is used to communicate with all devices on a particular network or subnet.
IPv4 addresses are logical addresses best concieved of as a string of 32 bits (IPv4). IP addresses are composed of two parts, a network portion and a host portion. The subnet mask indicates how many bits in an IP address are used to identify the IP network, and how many bits are used to identify the host. The broadcast address uses all binary 1's in the host portion of the IP address. The last address in any IP address range is the broadcast address. Any IP communications transmitted to the destination address of the broadcast address is sent to all end stations (not network devices) on the same IP network, that is, all hosts that are part of the same IP address subnet range are included in the communication.
| SUBNET: 192.168.1.64/26 | OCTET 1 | OCTET 2 | OCTET 3 | OCTET 4 | NOTES |
|---|---|---|---|---|---|
| Decimal | 192 | 168 | 1 | 127 | Last address in the IP Address Range used for "All Local Hosts" communication |
| Binary | 11000000 | 10101000 | 00000001 | 01111111 |
Count the binary bits marked in blue for the network portion of the address and you will see that there are 26 bits for the network and six bits for the host in red. The 26 bits matches the /26 of the CIDR mask at the top left of the table. Note that all the RED bits are 1's. When you look at it in binary, it's easy to see that the network portion extends into the fourth octet in the address, and that the host bits are all set to 1. This is not so obvious from decimal unless you are able to recognize the magical decimal numbers that match certain patterns of binary bits.