IT - Network Operations - Senior Systems Administrator

Island Capital Group LLC•Irving, TX

About The Position

The Senior Systems Administrator / Senior Network Administrator manages enterprise infrastructure across security operations, cloud platforms, network routing, firewall and VPN services, monitoring systems, server patching, certificate and DNS workflows, and vendor support operations. The role combines hands-on administration with incident triage, technical documentation, support-case ownership, procurement and renewal coordination, and recurring maintenance execution. Recent activity shows direct ownership or active participation in Microsoft Sentinel and Defender monitoring, Cisco router and contract support, Constellix DNS changes, Aruba/HPE networking, Azure infrastructure, Equinix network-edge notices, GoAnywhere renewal support, printer security standards, and monthly server patching processes.

Requirements

Proven experience to implement and operate a minimum of five of the following: Windows Server 2012 R2 Active Directory (Users/Computers/DNS/DHCP/Group Policy), Server Management (physical server builds from scratch, cluster configuration, virtual machine deployment from template, hardware parts replacement / upgrades), VMWare Virtualization (build and deploy VMWare hosts, vCenter, vSwitching and HA connectivity to SAN and Network), Communications (SIP Lines, Cisco Call Manager, Cisco Unity, Cisco Jabber, Contact Call Center Express), Backup and Recovery (Veeam Backup and Replication, Backup Exec and iScalar 500 Library), Networking- Firewalls and Switching (VLAN, DMZ, Interface Tagging, Interface Configuration, Network Address Translation, Firewall Rules, VPN, Access Lists, Load Balancers), Storage Area Network (Array configuration, Storage Pool creation and management, attach hosts to SAN and provision storage, fiber switch configuration, disk replacement, NAS management, recover point appliances), Messaging Exchange 2013 / 2010 (SMTP connectors, DAG, mailbox database policies, Proof Point, Global Relay, Blackberry Work), System Center Configuration Manager (serve and desktop patching, image deployment, software deployment, MBAM integration, Distribution Points), Security Systems (Palo Alto, PGP Encryption, Sophos Encryption, Symantec Antivirus / DLP, Cisco Fire Power, Cyber Ark Identity Management, MBAM), IT Controls (Change Management, Incident Management, Audits).
10 years of previous server administration and / or network administration experience.

Responsibilities

Investigate and triage security alerts: Review high-severity Sentinel and Microsoft Defender notifications, validate legitimacy, document response status, and close or monitor recurring alerts as appropriate.
Maintain security analytics and reporting: Create, refine, and run KQL queries and workbooks for sign-in, identity, retention, ingestion, lockout, vulnerability, and operational monitoring use cases.
Support retention and cost decisions: Analyze Log Analytics retention options, analytics retention versus long-term retention, ingestion volume, and cost impacts for security data storage.
Administer Azure-hosted infrastructure: Support Azure infrastructure advisories, network security group policy compliance, virtual firewall dependencies, flow logging, and cloud network remediation tasks.
Coordinate firewall and VPN-impacting changes: Plan and communicate maintenance windows that may affect VPN connectivity, file-share access, and routing availability.
Maintain operational resilience: Review vendor maintenance notices and assess network impact for Equinix Network Edge and related infrastructure assets.
Manage Cisco routing platforms: Perform IOS XE image upgrades, validate install-mode boot state, confirm packages.conf/boot variables, collect show outputs, and coordinate with Cisco TAC or support assistants.
Resolve Cisco portal and entitlement issues: Work through Cisco Smart Account, contract access, CCW-Renewals, support case visibility, and software entitlement issues needed to obtain required IOS images or manage support records.
Support Cisco procurement/renewal lifecycle: Review Cisco order fulfillment and contract notification details, validate Smart Account assignment, track Cisco Catalyst 8200 service coverage, and coordinate with resellers such as GDT when contract visibility or device association is incorrect.
Maintain Cisco network service awareness: Support router, switch, VPLS data circuit, device, and subscription records as part of broader enterprise network administration.
Administer external DNS records: Use Constellix DNS as the company external DNS management platform, including domain and record updates when business, website, certificate, or redirect changes require DNS action.
Perform DigiCert DCV revalidation: Maintain and execute the DigiCert domain certificate revalidation procedure, including retrieving DCV tokens and updating _dnsauth CNAME records in Constellix.
Coordinate DNS changes with stakeholders: Schedule and perform CNAME changes with application or website owners, confirm timing, notify stakeholders when records are created or committed, and support post-change validation.
Document DNS procedures: Create or maintain KB documentation for Constellix and DigiCert workflows to support repeatable operations and reduce DNS change risk.
Administer Aruba/HPE networking: Work with HPE/Aruba support on AP/certificate issues, update captive portal certificate usage, review Aruba advisories, and coordinate HPE support/contract follow-up.
Monitor and respond to infrastructure alerts: Use monitoring tools to detect certificate, device, network, and system alarms; suppress or validate alerts during maintenance; and confirm health after changes.
Support telecom and legacy network services: Maintain awareness of DNS, firewall, and service dependencies for Cisco Expressway/voice and other infrastructure services documented in KBs.
Execute recurring server patching: Participate in monthly patch deployment work, including SCCM update group maintenance, Thursday-before-UAT update additions, pre/post checks, monitoring suppression, validation, and reporting.
Maintain secure endpoint and printer standards: Update printer hardening procedures, including protocols, TLS settings, SNMP communities, and scan-to-email behavior.
Track vulnerability remediation: Review vendor advisories and Defender vulnerability findings, and coordinate remediation paths across affected devices and platforms.
Manage support cases and renewals: Coordinate with Cisco, HPE/Aruba, CDW, GDT, Fortra/GoAnywhere, Equinix, DigiCert, and other vendors to resolve support, licensing, portal, renewal, and maintenance issues.
Assist business and finance stakeholders: Support invoice/portal-access issues or operational requests that affect IT services and vendor account access.
Create and update KBs and runbooks: Develop practical documentation for repeatable administration, security, patching, DNS, certificate, and infrastructure tasks.