What is the symptom of an IP address conflict on a host?

• A. The system reports 'IP address already in use' during boot
• B. DNS server unreachable
• C. The router LED blinks
• D. The DHCP server responds with an offer

Answer: (A)

An IP address conflict happens when two devices on the same network try to use the exact same IP address. The host checks for duplicates as it starts up by using ARP to see who owns that address. If another device answers or a duplicate is detected, the operating system surfaces a warning like “IP address already in use.” That message directly signals that the address is being claimed by more than one device, which is exactly what a conflict looks like to the user.

The other options aren’t about address duplication: DNS server unreachable points to name resolution problems, not that two devices share an address; a router LED blinking can indicate normal traffic or link status, not a conflict; the DHCP server offering an address means the client is obtaining an IP from DHCP, which doesn’t imply a duplicate address issue.