City Guilds Model Questions Vol1 2018 Information Technology Question 15

In a small office network, five PCs (PC1-PC5) are connected to an 8‑port Ethernet switch, which in turn is linked to a router that provides Internet access. All PCs use static IPv4 addresses in the 192.168.1.0/24 network with gateway 192.168.1.1 (the router). The observed behaviour is: - PC1 can ping the router and access the Internet. - PC2 can ping PC1 but cannot ping the router or reach the Internet. - PC3 can ping the router but cannot reach the Internet. - PC4 cannot ping any other device, including the router. - PC5 can access the Internet but cannot ping PC3. A network administrator discovers that the router's firewall has the following rules: 1. Block all ICMP (ping) traffic from IP addresses ending in .20 and .40. 2. Block all outbound traffic (including HTTP, HTTPS, etc.) from the IP address ending in .30. 3. Allow all other traffic. Assuming the hardware (switch, cables, and PCs) is functioning correctly, identify the single faulty component or configuration that best explains all the symptoms, and justify your answer.