hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Is troubleshooting a DHCPv4 issue where a router…
A network engineer is troubleshooting a DHCPv4 issue where a router configured as a DHCP server is not assigning addresses from a pool to clients on a specific VLAN. The pool is configured with 'network 10.1.1.0 255.255.255.0' and 'default-router 10.1.1.1'. The router's interface Gi0/0.10 (subinterface) has encapsulation dot1Q 10 and IP 10.1.1.1/24. Clients send DISCOVER messages, but the router does not respond. The engineer notices that the router has multiple DHCP pools configured. What is the most likely cause?
⚠ Common exam trap
Cisco often tests the VRF-aware DHCP concept by presenting a scenario where a DHCP server has multiple pools and clients are not getting addresses, leading candidates to incorrectly suspect missing helper addresses or global DHCP commands, when the real issue is a VRF mismatch between the pool and the interface.
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
✓
The DHCP pool is configured under a VRF, but the interface is not in that VRF.
The router has multiple DHCP pools configured, and the pool for VLAN 10 is likely bound to a VRF. When a DHCP pool is configured under a VRF, the router only responds to DHCP DISCOVER messages received on interfaces that belong to that same VRF. Since the subinterface Gi0/0.10 is not in the VRF, the router ignores the client broadcasts, even though the IP address and subnet match the pool.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The DHCP pool is configured under a VRF, but the interface is not in that VRF.
Why this is correct
Correct because if the pool is defined with 'vrf <name>', it will only respond to DHCP requests on interfaces belonging to that VRF; the subinterface is not in any VRF, so the pool is ignored.
- ✗
The subinterface is missing the 'ip helper-address' command.
Why it's wrong here
Incorrect because the router is the DHCP server, so helper-address is not needed; the server responds directly to DISCOVER messages on the same subnet.
- ✗
The 'ip dhcp server' command is missing globally.
Why it's wrong here
Incorrect because the DHCP server process is enabled by default when a pool is configured; no global command is needed.
- ✗
The encapsulation dot1Q 10 is misconfigured, causing the router to not receive broadcasts.
Why it's wrong here
Incorrect because if the subinterface were misconfigured, it would not be up/up; the engineer would see the interface status as down.
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Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
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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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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