Senior Network Engineer

Thorn SDS; Corsham; On-site; GBP 65,000 - 75,000; Full time

Benefits offered by this job

25 days leave

Pension contributions

Group Life Insurance

Wellbeing services

Referral scheme

Training & certifications

Defence programme exposure

Enterprise networking tech exposure

Job summary

Thorn SDS in Corsham is seeking a Senior Network Engineer to design, maintain and optimise enterprise network infrastructure within a high‑security UK defence programme. You will deliver 2nd/3rd line support, tackle complex networking challenges and support secure deployments across fixed and deployable environments.

The role requires onsite work in Corsham with strong analytical, troubleshooting and communication skills, plus experience in enterprise routing/switching, Cisco tech, firewalls and

Qualifications

• Proven experience in enterprise LAN/WAN design, deployment and support.
• Strong knowledge of routing, switching and network security practices.
• Experience with firewalls, VPNs, and secure remote connectivity in regulated environments.
• Familiarity with VMware NSX or similar SDN tech is desirable.
• Ability to monitor, troubleshoot and optimize complex network infrastructure.
• Understanding of Layer 2/3/4 networking and performance analysis.
• Experience working in defence, MOD, or security-cleared environments.
• Ability to work onsite in Corsham with strong analytical and communication skills.

Responsibilities

• Provide advanced 2nd and 3rd line support across enterprise network infrastructure.
• Troubleshoot complex network issues and implement infrastructure improvements.
• Support secure deployments across fixed and deployable environments.
• Coordinate with service operations, resolver groups and engineering teams.
• Maintain network resilience and compliance with security policies.
• Support deployments across on‑premises and operational environments.
• Participate in ITIL-aligned incident, problem and change management processes.
• Contribute to the delivery of a deployable IT capability modernization programme.
• Collaborate with cross-functional teams to resolve technical issues.

Skills

Enterprise routing & switching

Cisco networking technologies

Firewalls & VPNs

Network monitoring & troubleshooting

Layer 4 dependencies & performance

Secure, regulations environments

Defence/MOD exposure

Tools

VMware NSX

Job description

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Cisco | Routing & Switching | Firewalls | VPN | VMware NSX | LAN/WAN | ITIL | Defence

Help secure the networks that support the UK’s critical defence operations.

Are you an experienced Network Engineer looking for a role where your expertise has a genuine operational impact?

We’re looking for a Senior Network Engineer to join a nationally significant UK Defence programme, supporting the secure, resilient network infrastructure that enables mission‑critical operations across the UK and overseas.

Working in one of the UK’s most secure IT environments, you’ll design, maintain and optimise enterprise network infrastructure while helping deliver the next generation of deployable IT services for the Ministry of Defence.

If you thrive on solving complex networking challenges and want to work with cutting‑edge technologies in an environment where reliability and security are paramount, we’d love to hear from you.

About Thorn SDS

Thorn SDS is a specialist Managed Service Provider headquartered in Alton, Hampshire. We partner with organisations across the Space, Defence and Security sectors, connecting exceptional technical professionals with some of the UK’s most challenging and rewarding engineering programmes.

About the Programme

You’ll be joining a major transformation programme modernising the Ministry of Defence’s deployable IT capability.

Replacing legacy communication and information systems with modern, secure and resilient platforms, the programme is delivering next-generation technology.

As part of the Through Life Support (TLS) team, you’ll help ensure these critical services remain secure, available and fully operational throughout their lifecycle.

The Role

As a Senior Network Engineer, you’ll provide advanced 2nd and 3rd line support across enterprise network infrastructure, ensuring the availability, performance and security of critical operational services.

Working alongside Service Operations, Resolver Groups and specialist engineering teams, you’ll troubleshoot complex network issues, implement infrastructure improvements and support secure deployments across both fixed and deployable environments.

This is an excellent opportunity for an experienced engineer who enjoys working with enterprise networking technologies in highly secure, mission‑critical environments.

What You’ll Be Doing

• Supporting and maintaining enterprise LAN, WAN and operational network infrastructure.
• Configuring, managing and troubleshooting routers, switches, firewalls and VPN technologies.
• Investigating and resolving complex Layer 2, Layer 3 and Layer 4 networking issues.
• Supporting Software Defined Networking technologies, including VMware NSX.
• Monitoring network performance, capacity and availability to ensure optimum service delivery.
• Implementing network upgrades, changes and security improvements.
• Supporting ITIL-aligned incident, problem and change management processes.
• Working closely with infrastructure, applications and security teams to resolve technical issues.
• Supporting deployments across both on‑premises and operational environments.
• Maintaining network resilience while ensuring compliance with MOD security policies and standards.

What We’re Looking For

You’ll also have excellent analytical, troubleshooting and communication skills and be comfortable working full‑time onsite in Corsham.

We’re particularly interested in candidates with experience in:

• Enterprise routing and switching (Layer 2 & Layer 3).
• Cisco networking technologies.
• Firewalls, VPNs and secure remote connectivity.
• VMware NSX or other Software Defined Networking technologies.
• Network monitoring, performance optimisation and troubleshooting.
• Layer 4 application dependencies and network performance analysis.
• Enterprise infrastructure within secure or highly regulated environments.
• Defence, MOD or other security‑sensitive environments (desirable).

What’s In It For You?

Alongside a competitive salary of £65,000–£75,000, you’ll receive:

• 25 days’ annual leave plus Bank Holidays.
• Employer pension contributions.
• Group Life Insurance.
• Wellbeing services including GP access, physiotherapy and lifestyle savings.
• Employee Referral Scheme.
• Funded training, certifications and ongoing professional development.
• The opportunity to work on one of the UK’s most significant defence technology programmes.
• Exposure to enterprise‑scale networking technologies within a highly secure environment.
• The chance to collaborate with experienced engineers on complex infrastructure projects that directly support UK defence capability.

Security Requirements

Applicants must have the right to work in the UK and either already hold, or be eligible to obtain, a high level of UK National Security Clearance.

Please note that, due to the nature of our work, nationality, previous nationalities and country of birth may affect eligibility for certain security‑cleared positions.