Start at the endpoint
When a user cannot connect, check power, cable, link light, interface state, wireless association and address assignment before blaming the server. Windows, Linux, macOS, Android and iOS expose the same basic facts through different screens or commands: address, mask or prefix, gateway, DNS and link status.
Read the symptom, not just the error
An APIPA address suggests DHCP failed. A valid address with no gateway points to local-only connectivity. An IP ping that works while a hostname fails points toward DNS. A link that is up but collecting CRC errors suggests a physical or duplex problem. Each result should change your next test.
Packet capture is a timeline
In a capture, filter for the conversation you are investigating. DHCP shows discover, offer, request and acknowledgement. DNS shows a query and response. TCP shows SYN, SYN-ACK and ACK before application data. ICMP echo and reply help separate reachability from application problems.
Use Cisco output as evidence
show interfaces reveals status, errors, speed and duplex. show ip interface brief gives a fast interface summary. show mac address-table explains switching knowledge. show ip route explains forwarding. show vlan and show power help isolate VLAN and PoE faults.