Complete BT & Fortinet Interview Preparation Guide

BT Core Values, Behaviours & STAR Technique

What are BT’s core values?

BT commonly focuses on being Personal, Simple and Brilliant: putting people first, keeping things clear, and delivering high standards.

What does Personal mean?

Being customer focused, taking ownership, communicating with empathy, and understanding the impact on users and the business.

What does Simple mean?

Making technical information easy to understand, avoiding unnecessary complexity, and choosing practical solutions.

What does Brilliant mean?

Aiming for high standards, continuous improvement, innovation, and delivering reliable outcomes.

Current / Recent Cyber Threats

What is ransomware?

Malware that encrypts systems or data and demands payment for recovery.

Common entry points:

• Phishing
• Weak credentials
• Exposed VPNs
• Vulnerable services

What is phishing?

Fake emails, websites or messages used to steal credentials or trick users into performing actions.

What is a Man-in-the-Middle attack?

An attacker intercepts traffic between two parties to steal or manipulate data.

Mitigations:

• HTTPS
• VPNs
• MFA
• Certificate validation

FortiGate Fundamentals

What is FortiGate?

Fortinet’s Next-Generation Firewall platform providing:

• Firewalling
• VPN
• SD-WAN
• IPS
• Antivirus
• Web Filtering
• Application Control
• Security Fabric integration

What is FortiOS?

The operating system running on FortiGate firewalls.

What is Security Fabric?

Fortinet’s integrated security ecosystem providing visibility, automation and coordinated security response.

What is FGCP?

FortiGate Clustering Protocol used for HA clustering.

Port used:

• TCP 702

What are VDOMs?

Virtual Domains allowing a single FortiGate to operate as multiple logical firewalls.

Difference between NAT mode and Transparent mode

NAT / Route Mode

• Operates at Layer 3
• Performs routing
• Supports NAT

Transparent Mode

• Operates more like a Layer 2 bridge
• Still performs inspection

Flow-based vs Proxy-based inspection

Flow-based

• Faster
• Lower latency

Proxy-based

• Deep inspection
• More resource intensive

What is SSL Deep Inspection?

FortiGate decrypts traffic, inspects it, then re-encrypts it.

Requires:

• Trusted CA certificate installed on endpoints

SD-WAN Deep Dive

What is SD-WAN?

Software-Defined WAN intelligently steers traffic across multiple WAN links based on:

• Latency
• Jitter
• Packet loss
• Policy

What is ADVPN?

Auto-Discovery VPN dynamically creates spoke-to-spoke tunnels.

Benefits:

• Lower latency
• Reduced hub load
• Better scalability

What are Performance SLAs?

Health checks monitoring:

• Latency
• Jitter
• Packet loss

Used for path selection.

IKEv2 and IPsec

Why is IKEv2 preferred over IKEv1?

IKEv2:

• More stable
• Better NAT traversal
• Fewer exchanges
• Supports MOBIKE

What is MOBIKE?

Allows IPsec tunnels to survive IP changes without full tunnel rebuilds.

IPsec Phase 1 vs Phase 2

Phase 1

Creates secure management channel.

Phase 2

Protects user traffic.

Recommended strong proposal

• AES-256
• SHA-256
• DH Group 14+
• PFS enabled

Recursive Routing

What does recursive routing mean?

The router performs another lookup to determine how to reach the BGP next-hop.

Common in:

• SD-WAN
• MPLS
• IPsec
• ADVPN

BGP Fundamentals

What is BGP?

Border Gateway Protocol is a path-vector routing protocol.

Why is BGP used in SD-WAN?

• Scalability
• Policy control
• Route reflectors

What is route refresh?

Allows BGP neighbours to resend routes without resetting the session.

What is graceful restart?

Allows temporary forwarding continuity while BGP restarts.

What is soft reconfiguration?

Stores received routes before policy application allowing policy changes without resetting sessions.

Common Troubleshooting Commands

diagnose debug flow
diagnose sniffer packet
diagnose sys session list
get system ha status

Behavioural Interview Questions

Tell me about a time you demonstrated ownership

Use a STAR example involving:

• Incident management
• Troubleshooting
• Communication
• Service restoration

Tell me about a time you simplified a technical issue

Explain how you translated technical detail into language understood by:

• Customers
• Managers
• Other engineers

Tell me about a mistake you made

Show:

• Accountability
• Learning
• Prevention improvements