Senior System Design Engineer (Network & Security) - Mechelen - Freelance / CDI

AlterSolutions

Mechelen, Flanders, Belgium permanent

Posted: April 13, 2026

Job Description

We are seeking a Senior System Design Engineer with strong experience in enterprise network and security infrastructures.

In this role, you will be responsible for the design, implementation, validation, operation, and optimisation of complex IT systems in a large enterprise environment.

You will act as a technical authority for network and security domains, working autonomously while collaborating with internal stakeholders to ensure stable, secure, and future‑proof platforms.

Key Responsibilities

• Analyse business and technical requirements and translate them into robust system designs
• Evaluate design options, trade‑offs, and benefits, ensuring alignment with enterprise standards
• Validate design compliance and support deployment to ensure requirements are fully met
• Design and optimise systems with focus on performance, capacity, availability, and scalability
• Contribute to technology evolution and continuous improvement initiatives
• Perform complex incident resolution and root cause analysis
• Maintain and update technical documentation
• Participate in on‑call rotations for the systems under your responsibility (when required)

Technical Scope

WAN & Security

• Fortinet technologies (FortiGate, FortiManager)
• SD‑WAN architectures
• BGP routing
• IPsec VPN technologies
• Firewall policy design and management
• Advanced troubleshooting and debugging

LAN

• HPE Aruba switching
• Cisco enterprise switching
• Core switching environments
• Aruba Central (on‑prem)
• VLANs, routing, redundancy and high availability

Wireless

• Aruba Access Points
• Aruba AirWave
• Enterprise Wi‑Fi design, optimisation and troubleshooting

General Networking

• Strong understanding of TCP/IP, routing and switching fundamentals
• Experience with enterprise monitoring and logging
• Knowledge of failover and high‑availability architectures

Required Experience & Skills

• 5+ years of experience as a system / network / infrastructure engineer
• Proven experience in enterprise network and security environments
• Strong hands‑on expertise with Fortinet and Aruba technologies
• Experience performing end‑to‑end design, validation, deployment and operations
• Solid troubleshooting skills and ability to work independently
• Experience with technical documentation and structured reporting
• Comfortable working in structured, large‑scale IT environments

Soft Skills

• Strong analytical and conceptual thinking
• Proactive mindset with the ability to take initiative
• Clear, structured and persuasive communication
• Result‑oriented and adaptable
• Administratively accurate and organised
• Strong collaboration skills

Languages

• English – Professional working proficiency (mandatory)

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