300-410 Infrastructure Services Practice Question
A network engineer is configuring a Cisco IOS router to act as a DHCP relay agent. The router interface GigabitEthernet0/0 is connected to a subnet with DHCP clients, and the DHCP server is located at 192.168.100.10. Which command must be applied to the interface to forward DHCP requests to the server?
⚠ Common exam trap
The trap here is thinking that enabling option 82 or specifying UDP forwarding alone is sufficient, but the 'ip helper-address' command is what actually forwards the requests.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ip helper-address 192.168.100.10
The 'ip helper-address' command on the client-facing interface is required to relay DHCP requests to a remote server. It forwards UDP broadcasts (including DHCP) to the specified IP address. Other commands either modify relay behavior or are for server configuration. This command is the fundamental step for DHCP relay.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ip dhcp relay information option
Why it's wrong here
This command enables the insertion of relay agent information option (option 82) into DHCP packets. It is used in conjunction with 'ip helper-address' but does not itself forward DHCP requests. It must be configured globally or on the interface, but without 'ip helper-address', requests are not relayed.
- ✗
ip dhcp pool RELAY_POOL
Why it's wrong here
The 'ip dhcp pool' command creates a DHCP pool for a DHCP server, not a relay agent. A relay agent does not need a pool configuration. This command would configure the router as a server, which is not the desired role in this scenario.
- ✗
ip forward-protocol udp 67
Why it's wrong here
The 'ip forward-protocol udp' command specifies which UDP protocols are forwarded when using 'ip helper-address'. By default, DHCP (UDP 67) is already forwarded, so this command is not required. It does not enable relay by itself; it only modifies the list of forwarded protocols.
- ✓
ip helper-address 192.168.100.10
Why this is correct
The 'ip helper-address' command configures the interface to forward UDP broadcasts, including DHCP requests, to the specified server address. It is the standard method for DHCP relay. When applied to the client-facing interface, the router will relay DHCP Discover messages to the server, allowing clients on that subnet to obtain addresses.
Visual reference
Go deeper
Related to this question
Learn chapter
Infrastructure Services: DHCP, NAT, and IPv6
Key term
DHCP Relay Configuration
A DHCP relay configuration allows a router to forward DHCP broadcast requests from clients on one subnet to a DHCP server on a different subnet, enabling centralized IP address management across multiple networks.
Key term
DHCP Client and Server
A DHCP client is any device that requests network configuration settings from a DHCP server, which automatically assigns IP addresses and other parameters to devices on a network.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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