Two core switches can be configured as a high-availability pair using VSX or stacking, with LAGs for inter-switch links and VLANs for Layer 2/Layer 3 traffic.

Step 1: Plan the Topology

Before configuration, determine the network topology:

• Decide whether to use VSX (Virtual Switching Extension) for independent control planes or stacking for a single logical switch.
• Identify primary and secondary roles if using VSX.
• Plan inter-switch links (ISL) using LAGs for redundancy.
• Define VLANs for access, transit, and routed traffic between the core switches and upstream networks .

Step 2: Configure Management Interfaces

• Assign IP addresses to the management VLAN on each switch.
• Ensure connectivity between switches for keepalive messages (VSX) or stack communication.
• Example for Aruba VSX:
  • Switch 1: VLAN 3999, IP 172.16.10.10/24
  • Switch 2: VLAN 3999, IP 172.16.10.11/24 .

Step 3: Configure Inter-Switch Links (LAG)

• Create a Link Aggregation Group (LAG) on both switches for the inter-switch link.
• Assign the LAG as the VSX data plane ISL or stack connection.
• Enable LACP active mode for dynamic link aggregation.
• Example:

  interface lag 128 no shutdown description VSX-ISL vlan trunk allowed all lacp mode active

Step 4: Configure VSX or Stack

• VSX:
  • Assign roles: one switch as primary, the other as secondary.
  • Configure VSX keepalive using the OOB management interface.
  • Synchronize features like STP, LLDP, and MC-LAG interfaces.
  • Example:

    vsx role primaryinter-switch-link lag 128keepalive peer 172.16.10.11 source 172.16.10.10vsx-sync vsx-global

• Stacking:
  • Assign stack member IDs and priorities.
  • Connect stack cables and power on switches.
  • Verify stack formation and master switch election .

Step 5: Configure VLANs and Routing

• Create VLANs for access and transit traffic.
• Configure Switch Virtual Interfaces (SVIs) for Layer 3 routing.
• Assign default gateways for hosts in each VLAN.
• Example for Nexus:

  interface vlan 10 ip address 192.168.1.1/24interface vlan 20 ip address 192.168.2.1/24ip route 0.0.0.0/0 10.0.0.2

Step 6: Verify and Save Configuration

• Check LAG status, VSX synchronization, or stack health.
• Test inter-VLAN routing and connectivity to upstream networks.
• Save the configuration to prevent loss after reboot:

  write memorycopy running-config startup-config

Key Considerations

• Always configure redundant paths to prevent single points of failure.
• Use MultiEdit or CLI for bulk configuration with syntax checking (Aruba CX).
• Monitor VSX or stack logs for errors during initial deployment.
• Ensure consistent VLAN and VRF assignments across both switches . By following these steps, your two core switches will operate as a resilient, high-availability pair capable of handling Layer 2 aggregation, inter-VLAN routing, and seamless failover.