Core Switch Configuration Replacement

Replacing a core switch requires careful planning, pre-configuration, and staged migration to minimize downtime and avoid IP conflicts.Pre-Replacement PlanningDocument Existing Network: Record all current switch models, software versions, VLANs, ACLs, PoE usage, uplinks, and routing configurations .Identify Critical Connections: Determine which devices and edge switches are most critical to network operations .Plan Maintenance Window: Schedule the replacement during low-traffic periods or a weekend to reduce impact .Prepare Rollback Plan: Keep old cables and configurations ready in case the migration fails .Pre-Configuration of the New SwitchLab Setup: Configure the new switch in a lab or isolated environment with VLANs, QoS policies, ACLs, and stacking configurations .Routing and SVIs: Pre-configure Layer 3 interfaces, SVIs, and routing protocols (OSPF, HSRP, etc.) but keep them in shutdown mode to prevent IP conflicts .Interconnects: Set up trunk links and interconnection VLANs for firewalls, routers, and BRASs if applicable .Verification: Test connectivity from the new switch to ensure configurations are correct before connecting to the live network .Migration ProcessDisconnect Old Switch: During the maintenance window, power down the old core switch.Physical Cable Migration: Move connections to the new switch, either all at once or VLAN by VLAN to reduce risk .Activate Interfaces: Bring up SVIs and routing interfaces on the new switch sequentially to avoid IP conflicts .Monitor Traffic: Verify that all critical services (voice, Wi-Fi, servers) are operational and that routing adjacencies are established .Post-Replacement VerificationCheck VLANs and PoE: Ensure all VLANs are functioning and powered devices receive adequate PoE .Routing and Connectivity: Confirm that routing protocols are stable and that the network can reach upstream devices and the internet .Monitoring: Use network monitoring tools or Cisco DNA Assurance to track performance and troubleshoot any issues .Optional Strategies to Minimize DowntimeParallel Deployment: Deploy the new switch alongside the old one and migrate links gradually, keeping the old switch as a temporary gateway .Use Extra Cables: Pre-run new cables to the new switch to avoid re-cabling during the maintenance window .Staged VLAN Cutover: Shut down one VLAN at a time on the old switch and bring it up on the new switch to reduce service disruption . By following these steps, you can replace and configure a core switch efficiently, ensuring minimal downtime, avoiding IP conflicts, and maintaining network stability throughout the migration process.