computer networks | Broadcasting

Question

why the limited broadcasting address is all 1's as all 1's should be the specific ip address of the last host in the network and not the address of all the host in the specific n/w. Please explain

Answer 1

The limited broadcast address is 255.255.255.255 and is defined to be all-ones. It is “limited” because it is never forwarded  across a router, unlike a directed broadcast which is a subnet directed broadcast.                                                                                                                                                                    A network-prefix-directed broadcast is composed of the network prefix of the IP address with a local part of all-ones.

For example, a Class A net broadcast address is net.255.255.255,  a Class B net broadcast address is net.net.255.255  and a Class C net broadcast address is net.net.net.255  where net is a byte of the network address.

Source : RFC 1812 - Requirements for IP Version 4 Routers section 5.3.5

• Local Broadcast IP – 255.255.255.255
  • Can be used to speak to everyone on the Local network
• Directed Broadcast – <Broadcast IP of each Subnet>
  • Can be used to speak to everyone on the Local network
  • Can be used to speak to everyone on a Foreign network