255.255 Broadcast on the Network 111111 distant network, directed broadcast Figure 6.39 Special IP addresses. Introduction to Telecommunications Network Engineering of special use of all zero and all ones addresses a host address, where all bits in the host part are either zero or one, must not be used. The IP address 0.0.0.0 is used by hosts being booted, but not after- ward. IP addresses for later use may be assigned by the network for the host while it is booted. An address where all bits in the network part are zero refers to the current network, typically a LAN. All hosts in the network receive the IP packet with address consisting of all 1's. If only the host part is all 1's the packet is received by all hosts in the network identified by the network address. 6.6.4.2 Subnetworks As seen earlier, all hosts in the network must have the same network number. A company that has one class C can have up to 254 hosts in its network and the use of these addresses have to be controlled over whole network, which may consist of multiple LANs. This could become a serious headache for network managers as the network grows and hosts are added and relocated. For easier management, a network can be divided into subnets SO that a com- pany's network still acts like a single network to the outside world. The net- work manager can decide to use, for example, two first digits in the host address section as a subnet address, as shown in Figure 6.40. Now he or she may divide his or her network into four subnets, each containing up to 62 (0 and 63 are not used) hosts. If, for example, the class C network address is 221.109.65.0, the hosts are numbered from 1 to 254 (excluding 0 and 255). The 2 bits in Figure 6.40 identify four subnets and their host address ranges are 1 to 63. With subnet digits a whole 8-bit host part has values 1 to 63 (subnet 0), 65 to 127 (subnet 1), 129 to 191 (subnet 2), and 32 bits, 4 bytes Subnet Class C Network address Subnet 1111111 000000 Example 11011101 0110110 100000 address 128, subnet 2 Host 44 Fig