A workstation boots with an error indicating the IP address is already in use. What is a likely cause?

A workstation boots with an error indicating the IP address is already in use. What is a likely cause?

• A. Two workstations have the same static IP address.
• B. One IP address was not reserved by DHCP.
• C. The DHCP server is down.
• D. ARP poisoning is active.

Answer: (A)

The main idea is an IP address conflict on the local network. When two devices try to use the same IPv4 address, the network stack detects that another device is already responding for that address, so the system flags that the IP is “in use” and stops configuring the NIC properly at boot. The scenario described matches the common case of two workstations configured with the same static IP. With static addresses, there’s no automatic check by a server to prevent duplicates, so both machines can claim the same address until ARP probes reveal the conflict, triggering the error message. Why the other options don’t fit as neatly: if the DHCP server were simply down, devices would typically fail to obtain an address or fall back to a link-local address rather than explicitly reporting that an address is already in use. If an IP isn’t reserved by DHCP, that doesn’t by itself create a collision unless another device is statically using that same IP. ARP poisoning could cause various misdirection issues, but the straightforward boot-time message about the address being in use is most directly explained by a duplicate static address on two devices. To fix it, assign unique IPs to each device (or rely on DHCP with proper address management and reservations), ensuring static addresses don’t clash with DHCP scopes.

The main idea is an IP address conflict on the local network. When two devices try to use the same IPv4 address, the network stack detects that another device is already responding for that address, so the system flags that the IP is “in use” and stops configuring the NIC properly at boot.

The scenario described matches the common case of two workstations configured with the same static IP. With static addresses, there’s no automatic check by a server to prevent duplicates, so both machines can claim the same address until ARP probes reveal the conflict, triggering the error message.

Why the other options don’t fit as neatly: if the DHCP server were simply down, devices would typically fail to obtain an address or fall back to a link-local address rather than explicitly reporting that an address is already in use. If an IP isn’t reserved by DHCP, that doesn’t by itself create a collision unless another device is statically using that same IP. ARP poisoning could cause various misdirection issues, but the straightforward boot-time message about the address being in use is most directly explained by a duplicate static address on two devices.

To fix it, assign unique IPs to each device (or rely on DHCP with proper address management and reservations), ensuring static addresses don’t clash with DHCP scopes.