Data Center Fabric Migration for Financial Services

Problem

The client operated a flat, three-tier data center network with undocumented dependencies, inconsistent VLAN assignments, and no segmentation between application tiers. Change windows regularly overran due to manual validation, and two recent outages were traced to configuration drift between redundant core switches. The network team had no programmatic way to audit configuration state or validate changes before deployment.

Approach

We started with a full discovery phase: extracted running configurations from all Nexus switches, normalized them into a structured inventory, and mapped every VLAN, SVI, and port-channel relationship. From this data, we produced L2/L3 topology diagrams and identified 40+ undocumented inter-VLAN dependencies. We designed a spine-leaf ACI fabric with EPG-based segmentation aligned to application tiers, then built a phased migration plan that moved workloads subnet-by-subnet with automated pre/post validation checks. Each migration window included rollback triggers tied to specific health metrics.

Results

• Zero unplanned downtime during 14-week migration
• 1,200+ endpoints migrated across 8 change windows
• 40+ undocumented network dependencies identified and resolved
• Change validation time reduced from 4 hours to 25 minutes through automation
• Full PCI-DSS network segmentation compliance achieved