Senior Network Engineer

The Senior Network Engineer owns the design, deployment, and day-to-day operation of all networking layers within Sesterce data centers - from top-of-rack switches to core routing, WAN connectivity and out-of-band management. Working closely with the SRE and infrastructure teams, you will be the technical authority on all things networking and a key contributor to our datacenter buildout projects., Network Architecture & Design

• Design and implement scalable, resilient data center network architectures (spine-leaf, BGP EVPN/VXLAN)
• Infiniband network architecture, multitenancy, ufm. Cumulus OS
• Specify and size network equipment for new DC buildouts and capacity expansions
• Security process on cve audit/remediation on switch, firewall

Deployment & Operations

• Deploy, configure and maintain switches, routers, firewalls and load balancers (Arista, Cisco, Juniper, or equivalent)
• Manage WAN and peering connectivity: BGP sessions, transit providers, IXP interconnects
• Configure and maintain out-of-band management (OOB) and console server infrastructure
• Perform network performance tuning, capacity planning and traffic engineering
• Handle structured cabling and fibre patching (LC, MPO/MTP) on the DC floor

Automation & Tooling

• Develop and maintain network automation scripts and playbooks (Python, Ansible, Nornir)
• Integrate network devices into monitoring and telemetry stacks (Grafana, Prometheus, gNMI/gRPC)
• Contribute to Infrastructure-as-Code practices (Git-based config management, CI/CD for network changes)

Incident Management & On-call

• Act as L3 escalation point for all network incidents
• Lead root-cause analysis and post-mortem processes following major incidents
• Participate in on-call rotation and ensure rapid resolution of production issues

Security & Compliance

• Enforce network security best practices: ACLs, micro-segmentation, DDoS mitigation
• Collaborate with the security team on compliance requirements (SOC 2, ISO 27001)
• Maintain up-to-date network diagrams and operational documentation

• Bachelor's degree or higher in Computer Science, Networking, Telecommunications or equivalent
• Minimum 5 years of professional experience in network engineering, with at least 2 years in a data center environment
• Proven experience designing and operating production spine-leaf fabrics at scale

Technical Skills

• Expert-level knowledge of routing and switching: BGP, OSPF, MPLS, EVPN/VXLAN, STP/RSTP
• Hands-on experience with major DC networking vendors (Arista EOS, Cisco NX-OS, Juniper Junos)
• Strong understanding of Linux networking: namespaces, bridges, bonding, VRFs, eBPF
• Experience with network automation tools: Python, Ansible, Netmiko, NAPALM, Nornir
• Familiarity with observability tooling: Grafana, Prometheus, ELK, streaming telemetry
• Knowledge of physical layer: fibre optics (DWDM, coherent), MPO/MTP cabling, OTDR testing
• InfiniBand networking: HDR/NDR fabric design and operation, RDMA/RoCE configuration, subnet manager (OpenSM / NVIDIA UFM), ibdiagnet troubleshooting - experience in AI/HPC GPU cluster interconnects is a strong plus
• Relevant certifications (CCNP/CCIE, JNCIP, ACE) are a strong advantage

Soft Skills

• Strong analytical mindset and ability to troubleshoot complex, multi-layer network issues
• Autonomous, rigorous and comfortable working under pressure in a production environment
• Excellent communication skills; able to present technical topics to non-technical stakeholders
• Collaborative team spirit - comfortable working across infrastructure, SRE and security teams
• Ownership mindset: you take problems end-to-end and see them through to resolution

Languages

• English: Fluent
• French is a plus

• Technically rich environment: high-density GPU clusters, ultra-low latency fabrics, cutting-edge hardware
• Real ownership and decision-making power over the network architecture
• Close-knit, high-calibre team with a culture of engineering excellence
• Fast career progression in a rapidly scaling company
• Compensation based on profile and experience

Rémunération : à partir de 50 000,00€ par an

Sesterce is a French company developing and operating critical computing infrastructure, specialised in high-density data centers dedicated to artificial intelligence. Co-founded by Youssef El Manssouri (CEO) and Anthony Tchakerian (Chairman), the company designs, builds and operates next-generation compute campuses across France and internationally. With sites in Valençe (Drôme), Hauts-de-France and Île-de-France, Sesterce embodies an ambitious industrial vision: converting France's decarbonised electricity into AI computing power, in the service of European digital sovereignty. We are looking for a Senior Network Engineer to design, build and operate the network fabric of our AI data centers, where reliability and ultra-low latency are non-negotiable.