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.

Key Responsibilities:

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

Job Requirements:

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 Centre
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