200-301 Question 381
Single answerA network engineer is configuring DHCP in a network with multiple subnets. A router is being used as a DHCP relay to forward DHCP requests to a centralized DHCP server located in a different subnet. After configuration, hosts in one subnet are unable to obtain IP addresses from the DHCP server. Which command should the engineer verify on the router acting as the DHCP relay to resolve the issue?
- A
ip helper-address
- B
ip dhcp excluded-address
- C
service dhcp
- D
ip dhcp pool
Show answer and explanation
Correct answer: A
Explanation
When a router is configured as a DHCP relay, it must be instructed to forward DHCP requests from clients to the DHCP server in a different subnet. This is achieved using the 'ip helper-address' command, which specifies the IP address of the DHCP server. Without this command, the router will not forward DHCP discovery packets, and the clients will fail to obtain IP addresses.
- A. Correct.
The 'ip helper-address' command is required to configure the router as a DHCP relay. It specifies the IP address of the DHCP server to which the router forwards DHCP requests.
- B. Incorrect.
The 'ip dhcp excluded-address' command is used to exclude certain IP addresses from being assigned by the DHCP server. While important for DHCP server configuration, it does not configure DHCP relay functionality.
- C. Incorrect.
The 'service dhcp' command enables the DHCP service on the router itself, which is unnecessary when the router is acting as a DHCP relay.
- D. Incorrect.
The 'ip dhcp pool' command defines a DHCP address pool on the router, making it a DHCP server. This is not relevant when the router is functioning as a relay.