CCNP Virtualization Practice Question
A network administrator is deploying Cisco ACI in a data center. The administrator must configure a bridge domain that allows Layer 2 connectivity between endpoints in the same tenant while also providing Layer 3 gateway services. The design requires that the bridge domain support both unicast routing and unknown unicast flooding. Which two settings must be enabled on the bridge domain to meet these requirements? (Choose two.)
⚠ Common exam trap
The trap here is assuming that ARP flooding is required for Layer 3 gateway services, when in fact unicast routing is the key setting, and confusing unknown unicast flooding with other flooding types.
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
✓
Enable unicast routing on the bridge domain.
To provide Layer 3 gateway services, the bridge domain must have unicast routing enabled so it can route between subnets. To support unknown unicast flooding, the bridge domain must have unknown unicast flooding enabled. These two settings directly address the scenario's requirements, while other features like ARP flooding, IGMP snooping, and DHCP relay serve different purposes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Enable unicast routing on the bridge domain.
Why this is correct
Enabling unicast routing on the bridge domain allows the ACI fabric to perform Layer 3 routing between subnets within the bridge domain and to external networks. This is required for the Layer 3 gateway services specified in the scenario, as the bridge domain acts as the default gateway for endpoints.
- ✗
Enable DHCP relay on the bridge domain.
Why it's wrong here
DHCP relay is used to forward DHCP requests from endpoints to a DHCP server. It is not related to enabling Layer 3 gateway services or unknown unicast flooding. While it may be configured in some designs, it does not satisfy the specific requirements of this scenario.
- ✗
Enable IGMP snooping on the bridge domain.
Why it's wrong here
IGMP snooping is used to optimize multicast traffic by limiting multicast floods to ports that have interested receivers. It does not provide Layer 3 gateway services or unknown unicast flooding. While it is a valid feature, it is not relevant to the stated requirements.
- ✗
Enable ARP flooding on the bridge domain.
Why it's wrong here
ARP flooding is used to handle ARP requests when the fabric does not have a proxy ARP entry. While it can be part of some designs, it is not a requirement for enabling Layer 3 gateway services or unknown unicast flooding. Enabling it unnecessarily can increase broadcast traffic and is not mandated by the scenario.
- ✓
Enable unknown unicast flooding on the bridge domain.
Why this is correct
Enabling unknown unicast flooding ensures that frames with unknown destination MAC addresses are flooded within the bridge domain. This meets the design requirement for unknown unicast flooding, which is often needed when the fabric has not yet learned all endpoint locations.
Visual reference
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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
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.