Firewall Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Before your Firewall Engineer interview, it helps to see the questions from the interviewer's side. We have picked eight from our set of 12 and added the reason each one gets asked.

Eight Firewall Engineer interview questions, and what the interviewer is thinking

1. What is the difference between a stateful firewall and a next-generation firewall, and what would you enable on the latter?

Why they ask: To check you understand modern firewall capabilities.

2. How would you carry out a firewall rule review, and what would you look for?

Why they ask: To test your approach to maintaining a clean, secure rule base.

3. How do you design network segmentation and firewall zones for a typical organisation?

Why they ask: To check you can apply security architecture principles at the firewall layer.

4. Explain NAT and the different ways you would use it on a firewall, including the issues it can create for troubleshooting.

Why they ask: To test core networking knowledge relevant to firewall work.

5. How do you configure and secure site-to-site and remote access VPNs?

Why they ask: To test practical VPN knowledge, which is core to firewall engineering.

6. A critical vulnerability is announced in your firewall vendor's VPN gateway, with reports of active exploitation. What do you do?

Why they ask: To test emergency change, patching and incident response judgement.

7. Tell me about a time you cleaned up or migrated a firewall rule base. What was the outcome?

Why they ask: To test practical experience delivering firewall projects safely.

8. Why do you want to be a firewall engineer, and what does a typical week look like?

Why they ask: To check you understand and are suited to the role.

A sample answer to question 1

What is the difference between a stateful firewall and a next-generation firewall, and what would you enable on the latter?

A stateful firewall tracks the state of connections, so return traffic for permitted outbound sessions is allowed automatically and unsolicited inbound traffic is dropped, based on addresses, ports and protocols. A next-generation firewall adds application awareness, so it identifies traffic by application, such as Microsoft 365 or Dropbox, regardless of port, and typically includes user identity integration, intrusion prevention, TLS inspection, URL filtering, malware and sandbox inspection and threat intelligence feeds. On vendors such as Palo Alto, Fortinet, Check Point or Cisco Secure Firewall, I would build policy around applications and users rather than only ports, enable intrusion prevention with sensible profiles in prevention mode after a tuning period, and use URL categories and DNS security to block known malicious destinations. I would also enable logging to the SIEM and check the performance impact of each feature against the hardware's rated throughput, because enabling everything can overload an appliance.

Common mistake to avoid: Enabling every feature without checking throughput; decrypting all traffic with no exclusions

Want the rest?

Full model answers, key points and common mistakes for all 12 questions are on the Firewall Engineer interview questions page. The first five are free, no sign-up needed.