L3 Network Engineer (CISCO) - Must have an active SC or DV Clearance - Must be willing to apply for DV if SC ClearedAn 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 ResponsibilitiesProvide 3rd line support for LAN and WAN environmentsManage escalated incidents from 1st and 2nd line teamsImplement approved changes to live systemsInstall, configure, maintain and troubleshoot routers, switches, firewalls and related cabling infrastructurePerform IOS and firmware upgrades on network devicesUpdate and maintain network design documentationOffer network advice and input to design changesSupport operations in multi-security tier and multi-tenant environmentsMandatory SkillsStrong experience in 3rd line network supportConfiguration and troubleshooting of CISCO devicesASA and Firepower firewall experienceFamiliarity with VMware NSX Firewall and SDWANUnderstanding of NGNIX and Linux systemsExperience in multi-tenant and high-security networksDesirable SkillsDocumentation of network changes and design updatesEffective collaboration with cross-functional teamsExperience supporting defence or military environmentsThis role is suited to an experienced and security-cleared net