I need help with applying this to a business that handles product distribution and works with hundreds of suppliers anf distributes to hundreds of subsidiary businesses. The company has about $1500$ employess and services customers ranging from residential to industrial. They wholesell industrial supplies. The network is setup with a hub and spoke WAN and $3$ LANs that are the headquarters, product wharehouse, and an example subsidiary office. Please help me with network subnetting and please help me to answer the questions below from a cybersecurity perspective with great detail.

Connection Security

a$.$ Explain how network defenses should be structured using layering, segmentation, and other controls to achieve maximum confidentiality, integrity, and availability $($CIA$)$

b$.$ Diagram common architecture models for simple secure systems, including components and interfaces of internetworking devices, according to current standards. To include plans for securing client devices $($all client devices appropriate for your company$)$ i$.$ Hardware ii$.$ Software $($operating systems and application$)$