We had a router running in a Proxmox VM peg the CPU last night. There is a slight chance I had Netflow enabled, but I’m almost positive I disabled it. It appears like one CPU was pegged out at 100% while the others we’re idling and the only thing that would have caused this would be NAT. It was seeing over 1 Gbps of traffic with only 2 CPU cores in Proxmox.
The graph, the part on the left, was prior to upgrading it to 4 cores so LibreNMS now makes it look like it was only 50% but it was double that. The part on the right is after I disabled NAT and added 2 more cores. It sure looks like NAT was only using one of the 2 cores.