Campus networks today face several key challenges:
#Hard to expand/upgrade cabling system - Traditional Ethernet-based campus networks require extensive copper cabling, which is difficult to expand and upgrade, leading to higher costs and complexity.
#Chimney networks hard to maintain - Many legacy campus networks operate in a chimney-style architecture (vertical silos of network systems), making it difficult to manage and integrate different services.
#Restriction of 100m makes network complex - While Ethernet has a 100m distance limit, modern fiber- based Passive Optical LAN (POL) solutions overcome this restriction, making this less of a challenge today.
#Devices are too large - Modern networking equipment is compact and modular, making device size less of a concern in today's campus networks.
Thus, the correct answers are A and D.