This 200-301 practice question tests your understanding of network services and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: dHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A DHCP server is located on a different VLAN from the clients. Which feature is required so the clients can still receive addresses?
DHCP snooping
Why wrong: DHCP snooping is a security feature, not the relay mechanism.
DHCP relay
Correct. DHCP relay enables cross-VLAN DHCP service.
Port security
Why wrong: Port security is unrelated to relaying DHCP requests.
NAT overload
Why wrong: NAT overload does not solve this broadcast-forwarding issue.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DHCP relay
DHCP relay forwards client broadcasts to a remote server as unicast, typically using ip helper-address on the Layer 3 interface.
Key principle: DHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DHCP snooping
Why it's wrong here
DHCP snooping is a security feature, not the relay mechanism.
When this WOULD be correct
In a scenario where a network administrator is asked about securing a DHCP environment, a question may ask how to prevent rogue DHCP servers while allowing legitimate ones. In this case, DHCP snooping would be the correct answer as it protects the network from unauthorized DHCP responses.
DHCP relay
Port security
Why it's wrong here
Port security is unrelated to relaying DHCP requests.
When this WOULD be correct
In a scenario where a question asks about securing a network by limiting the number of devices that can connect to a specific switch port, port security would be the correct answer. For example, if the question involves preventing unauthorized devices from accessing the network while allowing legitimate DHCP clients, port security would apply.
NAT overload
Why it's wrong here
NAT overload does not solve this broadcast-forwarding issue.
When this WOULD be correct
In a scenario where the question asks about enabling multiple internal devices to access the internet using a single public IP address, NAT overload would be the correct answer. This would involve a setup where clients need to communicate externally while conserving public IP addresses.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is correct
Correct. DHCP relay enables cross-VLAN DHCP service.
Why this is wrong here
DHCP snooping is a security feature that prevents unauthorized DHCP servers from offering IP addresses to clients. It does not facilitate communication between clients and a DHCP server located on a different VLAN.
★ When this WOULD be the correct answer
In a scenario where a network administrator is asked about securing a DHCP environment, a question may ask how to prevent rogue DHCP servers while allowing legitimate ones. In this case, DHCP snooping would be the correct answer as it protects the network from unauthorized DHCP responses.
Why candidates choose this
Candidates may choose this option because they associate DHCP snooping with DHCP functionality and security, mistakenly believing it plays a role in enabling clients to communicate with a DHCP server across VLANs.
Why this is wrong here
Port security is a feature that restricts the number of MAC addresses allowed on a switch port, primarily for security purposes. It does not facilitate communication between different VLANs or assist clients in obtaining DHCP addresses from a server on another VLAN.
★ When this WOULD be the correct answer
In a scenario where a question asks about securing a network by limiting the number of devices that can connect to a specific switch port, port security would be the correct answer. For example, if the question involves preventing unauthorized devices from accessing the network while allowing legitimate DHCP clients, port security would apply.
Why candidates choose this
Candidates may choose this option because they associate port security with network access control, mistakenly believing it relates to managing DHCP traffic across VLANs.
Why this is wrong here
NAT overload, also known as Port Address Translation (PAT), is used to allow multiple devices on a private network to share a single public IP address. It does not facilitate communication between clients and a DHCP server located on a different VLAN, which is the requirement of the question.
★ When this WOULD be the correct answer
In a scenario where the question asks about enabling multiple internal devices to access the internet using a single public IP address, NAT overload would be the correct answer. This would involve a setup where clients need to communicate externally while conserving public IP addresses.
Why candidates choose this
Candidates may confuse NAT overload with DHCP functionality, thinking that since both involve IP address management, NAT could somehow assist in DHCP address assignment across VLANs. This misconception can lead to selecting it as a viable option.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
A common exam trap is selecting DHCP snooping as the solution for clients on different VLANs to receive DHCP addresses. DHCP snooping is a security mechanism that filters DHCP messages to prevent rogue servers but does not forward DHCP broadcasts across VLANs. Another tempting but incorrect choice is port security, which controls MAC address access on switch ports but does not affect DHCP broadcast forwarding. NAT overload is unrelated to DHCP address assignment and only translates IP addresses for outbound traffic. The key misunderstanding is confusing DHCP relay’s role in forwarding broadcasts with security or address translation features.
Detailed technical explanation
DHCP relay is a critical feature in networks where DHCP clients and servers reside on different VLANs or subnets. Normally, DHCP clients broadcast requests to find a DHCP server, but broadcasts do not cross router interfaces by default. DHCP relay agents, typically configured on Layer 3 interfaces, intercept these broadcasts and forward them as unicast packets to the DHCP server's IP address. This mechanism ensures that clients on separate VLANs can still obtain IP addresses and configuration parameters from a centralized DHCP server. In Cisco networks, the DHCP relay function is implemented using the 'ip helper-address' command on the router or Layer 3 switch interface connected to the client VLAN. This command specifies the DHCP server's IP address to which the relay agent forwards DHCP requests. The relay agent listens for DHCP broadcast messages, encapsulates them into unicast packets, and sends them to the server. When the server replies, the relay agent forwards the response back to the client VLAN, enabling seamless IP address assignment across VLAN boundaries. A common exam trap involves confusing DHCP relay with DHCP snooping or other security features. DHCP snooping is designed to prevent rogue DHCP servers and does not facilitate cross-VLAN DHCP communication. Similarly, port security and NAT overload do not address the broadcast forwarding issue inherent in DHCP requests across VLANs. Understanding the specific role of DHCP relay in forwarding DHCP broadcasts as unicasts to remote servers is essential for correctly answering related CCNA questions and for practical network design.
Key takeaway
DHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet.
Real-world example
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Review dHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Services and Security — This question tests Network Services and Security — DHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet..
The correct answer is: DHCP relay — DHCP relay forwards client broadcasts to a remote server as unicast, typically using ip helper-address on the Layer 3 interface.
Review dHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet., then practise related 200-301 questions on the same topic to reinforce the concept.
DHCP relay forwards DHCP client broadcast requests as unicast packets to a DHCP server located on a different VLAN or subnet.
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Last reviewed: May 17, 2026
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