AlwaysOn VPN very slow speed

Question

Guys, did anyone come across the following problem, configured two servers with the RRAS role, only the VPN component is active, a scheme with one NIC interface is configured, the servers are connected through NLB, NLB is configured in Single Host mode, it turns out that the first VPN server is active, the second is passive, the VPN is configured and fully functional, the client tunnel of the device work without problems, all the hosts of the local network where the VPN client is connected are available. BUT there is a big problem with the data transfer speed, the upload speed is terribly low, 300 kb / s, the upload speed is higher - 5 mb / s, but still much lower than the total speed of the Internet channel. I also measured the speed to the VPN server bypassing the VPN channel, and the iperf shows excellent speed. VMs are installed on vCloud, access of remote clients is configured for a white IP, which is forwarded by the DNAT rule through the FortiGate gateway.

Answer 1

@Denis Tsareg Hi,

Thank you for posting in Q&A!

Since the slow performance issue is complex and there's no error message occurred for us to analyze. It only can be solved by analyzing the network packets. On the forum, we can only provide some general suggestions for your reference:
https://www.ivpn.net/knowledgebase/66/My-VPN-is-slow-what-can-I-do-to-make-it-faster.html

Besides, I would also suggest you contact Microsoft Customer Support and Services where more in-depth investigation can be done so that you would get a more satisfying explanation and solution to this issue. 
Global Customer Service phone numbers 
https://support.microsoft.com/en-us/gp/customer-service-phone-numbers

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Answer 2

I'll chime in here with the same issue. I'm using a Dell Latitude 7480 laptop connected to a Remote Access server on a VMware VM with Server 2016. The Dell Latitude is running on a home network connection (Eero wifi/firewall with 1Gb/s symmetric internet connection). The RA server traffic passes through a Palo Alto next-gen firewall on the other end with plenty of bandwidth to the internet.

I can get a consistent 23 Mbit/sec when using the wired network connection on the Latitude 7480 laptop where it only runs 5.5 Mbit/sec when on the wifi. Network interfaces are a wired Intel I219-LM and an Intel dual-band wireless-AC 8265.

For comparison, the same Dell Latitude 7480 using our Palo Alto GlobalProtect VPN can get 60 Mbit/sec with the wifi connection or 69 Mbit/sec over the wired connection.

Clearly the network device and driver can handle higher throughput, but the Always-On VPN cannot. Many of us would appreciate some tuning parameters to improve Always-On VPN performance.