Uneven CPU Load Distribution on FortiGate VM02 Across Clusters

[5q46n2te8jPWJY]

Hello Fortinet Community,

I am experiencing an issue with CPU utilization on one of my FortiGate VM02 instances. I have two clusters, both configured similarly, but their CPU load behavior differs significantly.

1. Cluster 1 (Normal Behavior):
   The CPU load is distributed evenly across both cores during IPsec operations, as shown in the output of the # diagnose vpn ipsec cpu command:

# diagnose vpn ipsec cpu
Software crypto CPU distributions:
CPU#            enc             dec-in          dec             dec-out         
0               18524077877     0               7856389447      7856389447      
1               18703560081     0               198249897       198249897

• Cluster 2 (Problematic Behavior):
  On the second cluster, the load is uneven and concentrated on a single core, which is causing performance concerns. Below is the output for the same command:

# diagnose vpn ipsec cpu
Software crypto CPU distributions:
CPU#            enc             dec-in          dec             dec-out         
0               1334517         0               0               0               
1               2208255         0               11464826        11464826

The uneven load on Cluster 2 results in one core being underutilized while the other handles all the decryption tasks. This behavior seems suboptimal compared to Cluster 1.

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Additional Information:

• FortiOS Version: 7.4
• Environment: VM02 running on Xen
• Configuration Parity: Both clusters are set up identically in terms of IPsec settings, general configurations and hypervisor configurations.

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My Questions:

1. What could be causing the uneven CPU load distribution on Cluster 2?
2. Are there any specific configurations or settings I should verify to ensure proper load balancing across cores?

Thank you in advance for your assistance!