189

Network Address

The network address is a standard way to refer to a network. For example, you could refer to the network inside the circle in Figure 6-9 as “the 10.0.0.0 network.” This is a much more convenient and descriptive way to refer to the network than using a term like “the first net-work.” All hosts in the 10.0.0.0 network will have the same network bits.

Figure 6-9             Network, Broadcast, and Host Addresses

Network                               Host

		Network Address
10	0	0	0
00001010	00000000	00000000	00000000
		Broadcast Address
																	10.0.0.253
10	0	0	255	10.0.0.3
00001010	00000000	00000000	11111111
															10.0.0.1
				10.0.0.2
		Host Address
10	0	0	1
00001010	00000000	00000000	00000001

This address cannot be assigned to a device and is, therefore, not used as an address for communication in the network. It is only used as a reference to the network. Within the IPv4 address range of a network, the lowest address is reserved for the network address. This address has a 0 for each host bit in the host portion of the address.

Broadcast Address

The IPv4 broadcast address within a network is the directed broadcast address. Unlike the network address, this address is used in communication to all the hosts in a network. This special address for each network allows a single packet to communicate to all the hosts in that network. To send data to all hosts in a network, a host can send a single packet that is addressed to the broadcast address of the network. For example in Figure 6-9 in the preced-ing section, to communicate with all the hosts in this network, use a destination address 10.0.0.255, which is the broadcast address for the network.

The broadcast address uses the highest address in the network range. This is the address in which the bits in the host portion are all 1s. For the network 10.0.0.0 with 24 network bits in Figure 6-9, the broadcast address would be 10.0.0.255.

Host Addresses

As described previously, every end device requires a unique unicast address to deliver a packet to that host. In IPv4 addresses, you can assign the values between the network address and the broadcast address to the devices in that network. These are called the host addresses.