The VPN speeds on the RT-AC88U are very slow when compared to HND CPU routers. I've had up to two HD TVs streaming at the same time over the VPN Client tunnel with no issues on a 200/100 Mbps fiber line.
I have been using 5 OpenVPN Clients running concurrently on an RT-AC88U while developing x3mRouting
. The project can help eliminate the need to manually swap VPN Clients.
The higher the encryption level, the harder the CPU has to work. I sometimes encounter low speeds on my Fire TV in hotel WIFI while traveling. For streaming traffic, the no encryption setting works fine and helps resolve buffering issues. AES-128-GCM cipher should give you the best performance when using encryption.
Many variables to OpenVPN performance
: CPU, encryption level, distance to server and ISP bandwidth.
openvpn --genkey --secret /tmp/secret
time openvpn --test-crypto --secret /tmp/secret --verb 0 --tun-mtu 20000 --cipher aes-128-gcm
Tue Jun 4 21:02:21 2019 disabling NCP mode (--ncp-disable) because not in P2MP client or server mode
real 0m 24.15s
user 0m 23.66s
sys 0m 0.34s
Comparing two routers:
( 3200 / execution_time_seconds ) = Projected Maximum OpenVPN Performance in Mbps
Asuswrt-Merlin RT-AX88U @ 1.88 GHz HND
Asuswrt-Merlin RT-AC88U @ 1.4 GHz ARM
AES-128-GCM: 3200/2.71 = 1181 Mbps
AES-128-CBC: 3200/3.21 = 996 Mbps
AES-128-GCM: 3200/24.15 = 132.51 Mbps
AES-128-CBC: 3200/20.58 = 155.49 Mbps
And the winner is....RT-AX88U!