Are you an experienced Network Engineer ready to take ownership of complex, secure network environments?Sopra Steria is delivering a unique solution from the ground up for the Defence sector, integrating infrastructure and applications within highly secure, mission-critical environments. This is an opportunity to make a genuine impact, contribute to complex technical solutions, and work on a nationally significant programme that few organisations can offer exposure to.For someone motivated by purpose, scale, and technical complexity, this role offers the chance to see your work directly contribute to outcomes that really matter.This role requires full-time, on-site working in Hertfordshire.What you will be doing:Deliver expert L2/L3 support for a complex, multi-site enterprise network, resolving incidents and minimising service disruption.Configure and maintain Cisco network infrastructure, including switches, routers, and core connectivity services.Support and optimise F5 application delivery and load balancing platforms to ensure availability, performance, and resilience.Administer Fortinet firewalls and security services, including policy management, VPN configuration, and security compliance changes.Execute planned network changes, upgrades, and site deployments while adhering to change control and security standards.Maintain low-level designs, technical documentation, and operational procedures, while supporting wider project delivery and continuous improvement ..... full job details .....