Senior Network Engineer

Our client, a prominent player in the Defence & Security sector, is seeking a Security Cleared Senior Network Engineer on a contract basis to support the delivery and optimisation of Cisco ISE (Identity Services Engine) and enterprise wireless (Catalyst 9800) platforms. This hands-on role focuses on engineering, troubleshooting, and implementation, particularly across secure network access (802.1X), policy enforcement, and wireless integration. You will play a key role in resolving complex issues, supporting upgrades, and ensuring stable, secure operation of critical network services., * Lead the design, build, and replacement of legacy Cisco Wireless infrastructure with modern Cisco Catalyst 9800 WLC architecture, ensuring scalable, resilient, and high-performance wireless services

• Define and deliver end-to-end wireless migration strategies, including planning, staging, cutover execution, and post-implementation optimisation
• Architect and implement high-availability 9800 WLC deployments (SSO, redundancy models), ensuring minimal service disruption and operational resilience
• Design and implement enterprise wireless solutions, including SSID segmentation, policy profiles, VLAN mapping, RF optimisation, and seamless roaming
• Own the design, upgrade, and lifecycle management of Cisco ISE environments, including version upgrades, patching strategies, backup/restore, and HA topology improvements
• Optimise ISE policy frameworks, including authentication and authorisation policies, profiling, posture, and identity-based access control
• Design and enhance secure network access solutions leveraging 802.1X and MAB across both wired and wireless environments
• Drive performance improvements and service optimisation across wireless and AAA infrastructure, identifying bottlenecks and implementing streamlined, scalable solutions
• Troubleshoot complex authentication and connectivity issues, utilising packet capture and deep protocol analysis (Wireshark, TCPdump)
• Support change and release activities, ensuring adherence to governance and documentation standards
• Manage and escalate issues to vendors (e.g. Cisco TAC) where required
• Produce clear and accurate technical documentation, runbooks, and support artefacts

• Security clearance (SC cleared or the ability to become SC cleared)
• Strong understanding of TCP/IP and OSI model fundamentals
• Experience with VLANs, trunking, inter-VLAN routing, DHCP, DNS, NTP, BGP, OSPF, EIGRP
• Solid grounding in network security (AAA, segmentation, firewall troubleshooting)
• Ability to perform packet-level troubleshooting
• Strong experience deploying and supporting Cisco ISE in enterprise environments
• Expertise in 802.1X (wired and wireless), MAB, RADIUS authentication flows, and policy enforcement
• Deep understanding of CAPWAP, AP join process, and mobility/roaming in Cisco Catalyst 9800 (IOS-XE) WLCs
• Experience with RF design (RRM, DCA, channel/power tuning), high-density wireless environments, FlexConnect and local mode deployments
• Strong knowledge of WPA2/WPA3 Enterprise and integration with ISE (802.1X, MAB, role-based access)

Desirable Skills:

• Experience with Cisco DNA Center
• Experience with ForcePoint Firewalls
• Suitable business and/or technical leadership skills in technology consulting
• Basic automation or API exposure (ISE/IOS-XE REST APIs)
• Relevant certifications such as CCNP Enterprise, CCNP Security, Cisco ISE Specialist, CWNA/CWNP

Soft Skills:

• Ability to diagnose cross-platform issues between ISE, WLC, and switching infrastructure
• Strong incident troubleshooting under pressure
• Clear and structured documentation of configurations, policies, and workflows
• Experience working within change and release management processes
• Effective stakeholder communication
• Experience with vendor escalation and TAC case management