Triggered by a customer who had problems getting enough speed through an IPsec site-to-site VPN tunnel between FortiGate firewalls I decided to test different encryption/hashing algorithms to verify the network throughput. I used two FortiWiFi 90D firewalls that have an official IPsec VPN throughput of 1 Gbps. Using iperf I measured the transfer rates with no VPN tunnel as well as with different IPsec proposals.
I first ran into really slow performances which were related to the default “Software Switch” on the FortiGate. After deleting this type of logical switch, the VPN throughput was almost as expected.