Junior Network Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Before your Junior Network Engineer interview, it helps to see the questions from the interviewer's side. We have picked eight from our set of 16 and added the reason each one gets asked.

Eight Junior Network Engineer interview questions, and what the interviewer is thinking

1. What is a VLAN, why would you use one, and how do trunk and access ports differ?

Why they ask: A staple junior network question testing switching fundamentals.

2. Explain how DHCP works and what you would check if a client gets a 169.254 address.

Why they ask: To test knowledge of core services and diagnostics.

3. What is the difference between a switch, a router and a firewall, and where does each sit in a typical office network?

Why they ask: To confirm basic device roles and network design understanding.

4. What is NAT, and what is the difference between static NAT, dynamic NAT and PAT?

Why they ask: To test understanding of IP addressing beyond subnetting.

5. What is Spanning Tree Protocol, and what problem does it solve?

Why they ask: To check understanding of loop prevention in switched networks.

6. You are told a branch office has lost connectivity to head office. What are your first steps?

Why they ask: To assess triage and escalation as a junior.

7. Tell me about a time you worked through a technical problem you did not initially know how to solve.

Why they ask: To assess problem-solving and learning approach.

8. Why do you want to be a network engineer, and what network certifications or skills are you working towards?

Why they ask: To check motivation and development plans.

A sample answer to question 1

What is a VLAN, why would you use one, and how do trunk and access ports differ?

A VLAN is a logical broadcast domain created on a switch, so devices can be grouped by function rather than physical location, for example staff, guest, voice and servers. It reduces broadcast traffic and improves security, because traffic between VLANs must pass through a router or layer 3 switch where policy can be applied. An access port belongs to a single VLAN and carries untagged traffic to an end device such as a PC. A trunk port carries traffic for several VLANs between switches or to a router or firewall, using 802.1Q tags to identify each frame, with a native VLAN carrying untagged traffic. On Cisco kit I would configure an access port with switchport mode access and switchport access vlan 20, and a trunk with switchport mode trunk plus an allowed VLAN list. I would also avoid leaving VLAN 1 in use and shut down unused ports.

Common mistake to avoid: Confusing VLANs with subnets; Leaving unused ports open

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Junior Network Engineer interview questions page. The first five are free, no sign-up needed.