Core switch HA ensures network redundancy by using active-passive or active-active supervisor modules, enabling seamless failover without disrupting traffic.

HA Modes and Supervisor Roles

Core switches typically support active-passive or active-active HA modes. In active-passive mode, one supervisor module is active while the other remains on standby, constantly monitoring the active module. If the active module fails, the standby automatically takes over, maintaining network traffic continuity. In active-active setups, both modules can process traffic, providing load balancing and redundancy simultaneously .

Step-by-Step HA Configuration

1. Prepare Network Components
   • Ensure all network links, VLANs, and routing paths are configured to allow the standby core switch to assume the primary role seamlessly.
   • Configure load balancers or DNS as needed to support HA failover .
2. Enable HA on Primary and Secondary Switches
   • Log into the Primary Core System Manager.
   • Navigate to Maintenance > HA Configuration > Service Configuration.
   • Enable High Availability and set the mode to Primary.
   • Repeat on the Secondary Core, setting the mode to Secondary and node status to Passive .
3. Configure Trusted Hosts
   • On the primary switch, copy the Local Server SSH Key.
   • On the secondary switch, add the primary as a trusted host by pasting the SSH key.
   • This ensures secure communication between HA nodes .
4. Link Aggregation and Redundancy
   • Use LACP (802.3ad) to aggregate multiple physical links between switches and HA devices for higher redundancy and performance.
   • Separate LACP groups for each HA device to prevent single points of failure .
5. Verify HA Status
   • Use commands like show system redundancy status or show module to confirm active and standby supervisor roles.
   • Ensure all modules report OK status and the standby module reflects HA-standby if HA switchover is enabled .

Best Practices

• Double Interconnect Links: For FortiSwitch or similar setups, double the interconnect links between distribution switches to ensure failover reliability .
• Nonstop Forwarding (NSF) and Stateful Switchover (SSO): Enable these features on Cisco platforms to maintain session information and minimize downtime during switchover .
• Regular Testing: Periodically perform manual switchover tests to validate HA functionality and failover behavior.
• Monitor Logs and Alerts: Continuously monitor HA events to detect early signs of hardware or software issues.

Summary

Configuring HA on core switches involves enabling HA on both primary and secondary nodes, setting up trusted host communication, aggregating links for redundancy, and verifying module status. Following best practices like LACP, SSO, and regular testing ensures minimal disruption and high network availability in case of failures .