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.
The IPv4 address space can be subdivided into five address classes called Class A, B, C, D and E. Each class consists of a contiguous subset of the overall IPv4 address range. IP Address Classes and Numbering. The values of the leftmost four bits of an IPv4 address determine its class.