Multi-site network

This SAÉ puts students in the shoes of a network integrator that has won a call for tenders: study and deliver the architecture of two e-commerce companies, UC Exchange and ABC Conseil, located on three sites in eastern France (Strasbourg, Nancy, Metz). Each head office has four departments, and the project requires a global IP addressing plan per site, a hierarchical switched architecture, high availability and inter-site connectivity. The work is split into three parts: LAN administration, network services implementation and operator interconnection (MPLS-VPN).

Carried out in a team of three (with Florence Cameron and Arthur Faity), the project was divided between the team members. My own contribution covers the LAN of the UC Exchange site in Strasbourg: I designed and configured the network core and all the switching, redundancy and internal routing mechanisms, up to the Internet exit through the ISP.

The network core I built is based on two switches linked by a port-channel (link aggregation), an enterprise-style architecture. The site has four business VLANs (IT department, Management, Finance department, Servers). To distribute the VLANs without configuring each device by hand, I set up a VTP server (left core switch in server mode, UCESS domain, the other switches as clients). Layer 2 fault tolerance is provided by MST spanning tree with two instances: the left core is root for instance 1, the right core for instance 2. Gateway redundancy is handled by VRRP on the two routers, each one master for a pair of VLANs and backup for the other.

Routing between the edge routers uses OSPF, with /30 interconnection links (a deliberate choice rather than static routes). The exit router performs NAT/PAT to communicate with the ISP. Host addressing is delegated to a DHCP server installed on a headless Debian VM, which hands out one range per VLAN and pushes a primary DNS, a secondary DNS and Google DNS as a fallback. Finally, I documented a walkthrough of a packet's path from a workstation to the Internet, showing the nominal path and the backup paths in case of failure.

Design and administer the LAN of one site of a multi-site company with a hierarchical switched architecture, ensuring high availability (link and gateway redundancy), internal routing and Internet connectivity, in line with the specification (MST, VRRP, NAT/PAT, per-VLAN addressing plan).