Senior Systems Administrator

Job Description

Job Description

Robert Half is partnering with our client in the Janesville area to hire an experienced Senior Systems Administrator to support and enhance a complex enterprise IT infrastructure. This is a hands-on senior-level role responsible for maintaining highly available server, cloud, storage, and network environments while serving as the primary escalation point for complex infrastructure issues. The ideal candidate brings deep Microsoft infrastructure expertise, strong networking experience, and a proactive approach to system reliability, security, and continuous improvement.

Responsibilities

• Administer, maintain, and optimize enterprise Windows Server environments, ensuring high availability, performance, and security.
• Manage Hyper-V virtualization infrastructure and support server lifecycle activities including deployments, upgrades, patching, and performance tuning.
• Administer Microsoft 365 services including Exchange Online, Teams, SharePoint, and related cloud technologies.
• Manage Azure infrastructure, subscriptions, identity services, and cloud resources.
• Maintain Active Directory, Group Policy, DNS, DHCP, and identity management services.
• Support enterprise storage infrastructure, including SAN environments and backup technologies.
• Configure, manage, and troubleshoot enterprise networking components including firewalls, switches, wireless networks, VPNs, and WAN connectivity.
• Administer Cisco Firepower and SonicWall firewalls, including security policies, VPN configuration, NAT, content filtering, and threat prevention.
• Manage Aruba switching infrastructure, VLANs, routing, network segmentation, and wireless environments utilizing Aruba and Ubiquiti technologies.
• Monitor infrastructure health, identify trends, and proactively resolve issues before they impact business operations.
• Lead troubleshooting efforts for complex infrastructure incidents and perform root cause analysis.
• Participate in infrastructure projects including migrations, upgrades, cloud initiatives, and technology implementations.
• Develop and maintain technical documentation, network diagrams, operational procedures, and configuration standards.
• Partner with security teams to implement infrastructure security best practices and remediation efforts.
• Identify opportunities to automate administrative tasks using PowerShell and other automation tools.
• Mentor junior team members and provide technical leadership on infrastructure initiatives.

• 7+ years of enterprise systems administration experience.
• Extensive experience administering Windows Server environments.
• Strong knowledge of Active Directory, Group Policy, DNS, DHCP, and Microsoft identity services.
• Experience supporting Microsoft 365 and Microsoft Azure environments.
• Hands-on experience administering Hyper-V virtualization.
• Strong enterprise networking experience including firewalls, switching, VPNs, wireless networking, and network troubleshooting.
• Experience supporting Cisco Firepower and SonicWall firewall platforms.
• Experience managing Aruba switching infrastructure.
• Experience supporting Aruba and Ubiquiti wireless environments.
• Experience with enterprise storage platforms and backup solutions.
• PowerShell scripting and automation experience.
• Excellent troubleshooting, communication, and problem-solving skills.
• Ability to manage multiple priorities in a fast-paced enterprise environment.
• Must be authorized to work in the United States without sponsorship.

Preferred Qualifications

• Experience administering enterprise SAN storage platforms such as HPE Nimble or similar technologies.
• Microsoft Intune administration experience.
• Experience with Microsoft Entra ID, Conditional Access, and cloud security solutions.
• VMware administration experience.
• Linux server administration experience.
• Experience with infrastructure monitoring and configuration management tools.
• Industry certifications such as Microsoft, Azure, Cisco, VMware, CompTIA, Aruba, or SonicWall certifications.
• Experience supporting highly available enterprise production environments.