220-1101 Question 121
Single answerExclusionsA technician is configuring a small office DHCP scope for the 192.168.10.0/24 network. The router uses 192.168.10.1, a network printer uses 192.168.10.20, and a file server uses 192.168.10.21. The DHCP scope is currently set to hand out addresses from 192.168.10.1 through 192.168.10.200, and users occasionally report IP conflicts with the printer and server. Which action should the technician take to prevent DHCP from assigning the statically configured device addresses while still allowing clients to receive automatic IP settings?
- A
Create exclusions for 192.168.10.1, 192.168.10.20, and 192.168.10.21 in the DHCP scope
- B
Configure a larger subnet mask so the DHCP server has more available addresses
- C
Enable APIPA on the printer and file server so they stop conflicting with DHCP clients
- D
Change the default gateway handed out by DHCP to 192.168.10.254
Show answer and explanation
Correct answer: A
Explanation
The best practice is to exclude any statically assigned addresses from the DHCP scope, or alternatively place the dynamic pool in a range that does not overlap with static devices. In this scenario, the DHCP pool includes addresses already assigned to infrastructure devices, so the DHCP server can accidentally lease those addresses and create conflicts. DHCP exclusions are specifically designed to prevent this. This aligns with standard TCP/IP addressing practice and common DHCP server configuration guidance from Microsoft and other enterprise networking documentation: infrastructure devices such as routers, printers, and servers should use reserved static addresses or reservations and be kept out of the dynamic assignment pool.
- A. Correct.
Correct. A DHCP exclusion range or excluded addresses prevents the DHCP server from leasing specific IP addresses within the scope. This is the appropriate way to protect statically assigned addresses such as the router, printer, and server from being offered to clients, which eliminates the source of the conflict while preserving automatic addressing for user devices.
- B. Incorrect.
Incorrect. Increasing the subnet size or changing the subnet mask does not solve the immediate issue that DHCP is allowed to lease addresses already in use by statically configured devices. The conflict is caused by overlapping static and dynamic assignments, not by a shortage of addresses.
- C. Incorrect.
Incorrect. APIPA assigns a 169.254.x.x address when a device cannot contact a DHCP server. It is not used to reserve addresses and would break connectivity for the printer and file server because they would no longer be on the office subnet. This reflects a common misconception between fallback addressing and DHCP scope management.
- D. Incorrect.
Incorrect. The default gateway setting tells clients which router to use for off-network traffic. Changing it does nothing to stop the DHCP server from leasing the printer's or server's addresses. In fact, changing the gateway incorrectly could create additional network connectivity problems.