A server is a computer or device on a network that manages network resources. Servers are often dedicated and they perform only their server tasks.
D (Network and subnet parts) . When using classful IP addressing concepts as described in Chapter 13, Analyzing Subnet Masks, addresses have three parts: network, subnet, and host. For addresses in a single classful network, the network parts must be identical for the numbers to be in the same network.
IP address can be a IPv4 or IPv6. IPv4 has 4 octets of 8 bits each. In IPv6, addresses are expressed as a series of eight 4-character hexadecimal numbers, which represent 16 bits each (for a total of 128 bits). each of these are called hextet as per IETF standard.