L3 Network Engineer (CISCO) - Must have an active SC Clearance An opportunity is available for an experienced L3 Network Engineer (CISCO) to join a committed team supporting UK Military systems. This is a fully on-site role in Portsmouth and requires strong 3rd line network support expertise, particularly in secure environments. You will work on incident resolution and system change implementation across LAN and WAN networks. Key Responsibilities Provide 3rd line support for LAN and WAN environments

Manage escalated incidents from 1st and 2nd line teams

Implement approved changes to live systems

Install, configure, maintain and troubleshoot Routers, Switches, Firewalls and related cabling infrastructure

Perform IOS and firmware upgrades on network devices

Update and maintain network design documentation

Offer network advice and input to design changes

Support operations in multi-security tier and multi-tenant environments

Mandatory Skills Strong experience in 3rd line network support

Configuration and troubleshooting of CISCO devices

ASA and Firepower Firewall experience

Familiarity with VMware NSX Firewall and SDWAN

Understanding of NGNIX and Linux systems

Experience in multi-tenant and high-security networks