Quick Answer
The answer is that both interfaces must be in the same VLAN. This is because HSRP operates at Layer 2, requiring all routers in the group to share a common broadcast domain so that hello messages (multicast to 224.0.0.2 on UDP 1985) can be exchanged and the virtual IP address can serve as the default gateway for hosts. Without the same VLAN, the switches cannot form an HSRP adjacency, as Layer 2 connectivity is a fundamental prerequisite. On the ENCOR 350-401 exam, this concept tests your understanding of how HSRP relies on VLAN boundaries for redundancy, often appearing in questions that try to trick you into thinking routing protocols or IP addressing alone suffice. A common trap is assuming HSRP can work across different VLANs with a Layer 3 link, but the protocol strictly requires the same VLAN for interface prerequisites. Memory tip: think “same VLAN, same broadcast, same HSRP group.”
This 350-401 practice question tests your understanding of infrastructure. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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 company has a requirement to provide redundancy for the default gateway on a subnet. Two switches are configured with HSRP. Which two interfaces on the switches must be in the same VLAN to form the HSRP group?
The interfaces must be on the same physical switch.
Why wrong: HSRP works across switches.
The interfaces must be Layer 2 switchports.
HSRP requires Layer 3 interfaces.
The interfaces must have the same IP address.
Why wrong: They use a virtual IP, not the same interface IP.
The interfaces must be in the same VLAN.
HSRP neighbors must be in the same VLAN.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The interfaces must be Layer 2 switchports.
HSRP (Hot Standby Router Protocol) requires that all routers participating in the same HSRP group share the same Layer 2 broadcast domain, which is defined by the VLAN. The interfaces on the switches must be in the same VLAN so that HSRP hello messages (multicast to 224.0.0.2 with UDP port 1985) can be exchanged and the virtual IP address can be used as the default gateway for hosts in that VLAN. Without the same VLAN, the switches cannot communicate at Layer 2, and HSRP adjacency will not form.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
The interfaces must be on the same physical switch.
Why it's wrong here
HSRP works across switches.
The interfaces must be Layer 2 switchports.
Why this is correct
HSRP requires Layer 3 interfaces.
Related concept
Read the scenario before looking for a memorised answer.
The interfaces must have the same IP address.
Why it's wrong here
They use a virtual IP, not the same interface IP.
The interfaces must be in the same VLAN.
Common exam traps
Cisco often tests the misconception that HSRP interfaces must be on the same physical switch (Option A) or must be Layer 2 ports (Option B), but the key requirement is that they share the same Layer 2 domain (VLAN) to exchange multicast hellos and maintain the virtual IP/MAC.
Detailed technical explanation
HSRP uses a virtual MAC address (0000.0c07.acXX, where XX is the group number in hex) that is shared by the active and standby routers. The active router responds to ARP requests for the virtual IP, and if it fails, the standby takes over with the same virtual MAC, ensuring seamless failover for hosts. In a switched environment, the VLAN defines the broadcast domain; without the same VLAN, HSRP hellos are isolated, and the group cannot elect an active router.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Infrastructure — study guide chapter
Learn the concepts, then practise the questions
Infrastructure practice questions
Targeted practice on this topic area only
All 350-401 questions
2,015 questions across all exam domains
ENCOR 350-401 study guide
Full concept coverage aligned to exam objectives
350-401 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 350-401 questions linked to Architecture.
Practise 350-401 questions linked to Enterprise Network Design.
Practise 350-401 questions linked to SD-Access Architecture.
Practise 350-401 questions linked to SD-WAN Architecture.
Practise 350-401 questions linked to QoS Architecture.
Practise 350-401 questions linked to Virtualization.
Practise 350-401 questions linked to Network Function Virtualization.
Practise 350-401 questions linked to Virtual Machines and Hypervisors.
Practise 350-401 questions linked to VRF and Path Isolation.
Practise 350-401 questions linked to Infrastructure.
Practise 350-401 questions linked to OSPF.
Practise 350-401 questions linked to BGP.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Infrastructure — This question tests Infrastructure — Read the scenario before looking for a memorised answer..
The correct answer is: The interfaces must be Layer 2 switchports. — HSRP (Hot Standby Router Protocol) requires that all routers participating in the same HSRP group share the same Layer 2 broadcast domain, which is defined by the VLAN. The interfaces on the switches must be in the same VLAN so that HSRP hello messages (multicast to 224.0.0.2 with UDP port 1985) can be exchanged and the virtual IP address can be used as the default gateway for hosts in that VLAN. Without the same VLAN, the switches cannot communicate at Layer 2, and HSRP adjacency will not form.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 11, 2026
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.