Senior Third Line Network Engineer

Salary: £75,000 - 75,000 per year

Requirements:

• Software Defined Networking experience with VMware NSX.
• Thorough and demonstrable understanding of Cisco Enterprise LAN environments at 3rd line support level, including deployment, administration, and troubleshooting.
• Ideally CCNP and CCDP level.
• Good understanding of WAN connectivity and routing protocols, with experience in implementing, configuring, and managing virtual and physical networking solutions.
• Hands-on experience in troubleshooting Layer 2/3 switching and routing.
• Hands-on experience in configuring and troubleshooting VPC, VDC, STP, BGP, OSPF, and other key mainstream protocols.
• Hands-on experience in configuring and troubleshooting Sidewinders and ASAv firewalls.
• Experience with ISR, 6800, 3750, and 3850 series platforms.
• Hands-on experience in configuring and troubleshooting Fortigate, Sonicwall, Palo Alto, ForcePoint, ASAv, and Juniper firewalls.
• Excellent communication and organisational skills, with the ability to work independently and autonomously.
• Ability to tackle complex problems and incidents.
• Experience in ITIL ICT service delivery on critical infrastructure.
• Experience working under pressure to meet deadlines while handling multiple priorities.
• Experience in patch management, including analysis and deployment.

Responsibilities:

• Provide complex fault rectification for incidents and support Problem Management, Continual Service Improvement (CSI), and occasional Change Request work on IT systems supporting key National Security outputs.
• Conduct reactive and proactive maintenance, primarily on High Side systems, and occasionally support lower classification systems.
• Respond to escalations from 2nd Line Engineers and other Resolver Groups, and carry out advanced troubleshooting to diagnose and rectify issues.
• Develop technical solutions to complex issues and problems.
• Liaise with stakeholders at all levels of seniority, including the customer.
• Resolve issues and problems within SLA levels and ensure KPIs are met.
• Ensure the Core Network estate is kept online and running smoothly, with incidents dealt with in a timely manner.
• Work with other resolver groups, original manufacturers, users, and suppliers to perform root cause analysis and provide technical solutions.
• Complete and record periodic maintenance of all systems using PPM and routine upgrading activities to stay ahead of obsolescence issues.
• Maintain and create documentation of system configuration changes and accurately record work in SD.
• Assist in the configuration, installation, and deployment of infrastructure components.
• Engage in infrastructure-related projects and CRs, contributing to implementation, build, and testing phases.

Technologies:

• Cisco
• FortiGate
• ICT
• Support
• ITIL
• LAN
• Network
• Security
• VMware
• AI
• Machine Learning

More:

We are Leidos UK & Europe, a growing company focused on making the world safer, healthier, and more efficient through technology, engineering, and science. We support critical capabilities and transformation across defence, healthcare, government, safety and security, and transportation. Based in Huntingdon, UK, this role supports core services on highly utilised systems in a secure environment. We offer a collaborative culture, meaningful careers, support for career goals, a healthy work-life balance, and a reward package that includes a contributory pension scheme, private medical insurance, 33 days annual leave, flexible benefits, and flexi-time. We also promote diversity and inclusion, flexible working, technical academies, career rotations, and career development plans.

last updated 34 week of 2026