Sr. Network Infrastructure Engineer

Date posted: August 6, 2026

Work Type: Contract 6 month opportunity with possibility for extension.

Job description:

Position Summary

Concordant LLC is seeking a hands-on Senior Network Infrastructure Engineer to support a phased infrastructure modernization engagement for a multi-site customer. This contractor will own the network-focused workstream: validating the current environment, developing a practical future-state design, evaluating and recommending replacement hardware, and leading the configuration, implementation, performance testing, and cutover of network infrastructure.

The environment includes multiple business locations, SonicWall and Sophos firewalls and site-to-site connectivity, switching and wireless infrastructure, VMware ESXi networking, on-premises Windows services, and Azure connectivity dependencies. The right candidate combines strong design judgment with disciplined implementation and troubleshooting skills. This is an execution-oriented role; the engineer must be comfortable working independently while coordinating closely with Concordant’s Azure/Windows engineer and project manager.

Key Responsibilities

• Validate discovery findings and document the current network topology, traffic flows, dependencies, constraints, risks, and performance bottlenecks across customer locations.
• Develop a right-sized target-state network design covering VLANs, segmentation, IP addressing, routing, switching, firewall policy, wireless, site-to-site VPNs, remote access, and resiliency.
• Review and improve SonicWall and Sophos firewall and VPN configurations, including rules, objects, NAT, routing, logging, and secure inter-site connectivity.
• Assess and configure switching and UniFi components, including VLAN assignments, trunks, uplinks, access ports, wireless network mappings, and management connectivity.
• Assess existing network hardware, software, licensing, lifecycle status, capacity, supportability, and replacement needs; translate findings into clear technical and operational requirements.
• Evaluate, size, and recommend firewalls, switches, wireless equipment, and related infrastructure from Sophos, SonicWall, Cisco, Fortinet, UniFi, or any other appropriate major vendor. Prepare bills of materials, licensing, support, and cost options; then lead ground-up configuration, staging, installation, migration, testing, validation, and documentation.
• Prepare implementation plans, configuration standards, rollback procedures, validation checklists, and concise as-built documentation needed for safe execution and support.
• Stage, implement, validate, and troubleshoot network changes across multiple sites while minimizing operational disruption.
• Coordinate Azure network connectivity with Concordant’s Azure/Windows engineer, including VPN, routing, DNS, network security, and hybrid connectivity dependencies.
• Support iterative file-services and storage performance testing; identify network-related throughput, latency, packet-loss, MTU, routing, or firewall constraints and tune where appropriate.
• Support VMware networking dependencies, including physical uplinks, NIC teaming, vSwitches, port groups, VLAN presentation, and connectivity validation.
• Provide focused cutover support, root-cause troubleshooting, knowledge transfer, and operational handoff to Concordant and the customer.

Required Qualifications

• 7+ years of hands-on network engineering experience, including responsibility for production design, implementation, and troubleshooting in small-to-midsize enterprise environments.
• Demonstrated expertise with SonicWall and Sophos firewalls, site-to-site VPNs, firewall policy, NAT, routing, logging, and troubleshooting.
• Demonstrated experience gathering requirements and independently selecting, sizing, designing, and deploying complete network environments across multiple major vendors, including building and configuring new infrastructure from the ground up.
• Strong practical knowledge of Layer 2 and Layer 3 networking, VLANs, trunking, spanning tree, subnetting, DHCP, DNS dependencies, static and dynamic routing, QoS, and network segmentation.
• Experience with managed switching and wireless platforms; direct UniFi experience is strongly preferred.
• Experience supporting VMware ESXi network connectivity, vSwitches, port groups, physical NICs, and VLAN integration.
• Working knowledge of Azure networking, including virtual networks, subnets, network secu…