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 answer would be sub-netting.The IP version 4 address is a 32 bit address which is written in dotted decimal format. The decimal or dot separates the 4 octets i.e. 8 bits are 01 octet. So in your example 1.4.145.x would be the IP addresses and 1.4.145.0 is the Network Identifier.