About Us

 

We are a French company specializing in the development and operation of critical computing infrastructures, with a focus on high-density data centers dedicated to artificial intelligence. In full growth mode, our mission is to design, build, and operate next-generation computing campuses across France and internationally — converting France's decarbonised electricity into AI computing power, in the service of European digital sovereignty. With sites in Valence (Drôme), Hauts-de-France and Île-de-France, our solutions power the most demanding AI workloads for leading clients in the industry. 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.

 

Your Responsibilities

As a Senior Network Engineer, you will own 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. 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).
• Architect InfiniBand networks with multitenancy and UFM on Cumulus OS.
• Specify and size network equipment for new DC buildouts and capacity expansions.
• Lead security processes including CVE audit and remediation on switches and firewalls.

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

 

Your Profile

• Education: Bachelor's degree or higher in Computer Science, Networking, Telecommunications, or equivalent.
• Experience: Minimum 5 years 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 Arista EOS, Cisco NX-OS, Juniper Junos; strong Linux networking skills (namespaces, bridges, bonding, VRFs, eBPF); experience with automation tools (Python, Ansible, Netmiko, NAPALM, Nornir); familiarity with observability tooling (Grafana, Prometheus, ELK, streaming telemetry); knowledge of fibre optics (DWDM, coherent), MPO/MTP cabling, OTDR testing. InfiniBand networking experience (HDR/NDR, RDMA/RoCE, OpenSM/NVIDIA UFM) is a strong plus. Certifications (CCNP/CCIE, JNCIP, ACE) are a strong advantage.
• Soft Skills: Strong analytical mindset, autonomous and rigorous under pressure, excellent communication skills with both technical and non-technical stakeholders, collaborative team spirit across infrastructure, SRE and security teams, and an ownership mindset — you take problems end-to-end.
• Languages: Fluent English required. French is a plus.

 

Why Join Us?

• A senior technical role at the core of France's most ambitious AI infrastructure programme.
• A technically rich environment: high-density GPU clusters, ultra-low latency fabrics, cutting-edge hardware.
• Real ownership and decision-making power over the network architecture.
• A close-knit, high-calibre team with a culture of engineering excellence.
• Fast career progression in a rapidly scaling company.
• Competitive compensation based on profile and experience, plus benefits: health insurance, meal vouchers, transport reimbursement.

 

How to Apply

Ready to take on the challenge? Don't hesitate — apply now! We're excited to meet you and build the future of AI infrastructure together. If you are a seasoned Network Engineer with a passion for high-performance and critical infrastructure, we invite you to apply. Please submit your resume and a cover letter to hr@sesterce.com. Include "Senior Network Engineer Application - [Your Name]" in the subject line.