SoftEther VPN User Forum

Posted: **Wed Dec 15, 2021 3:17 pm**

Hi everyone,

I'm running a SoftEther VPN server, version 9760, on RbPi. Since it's behind a firewall (and NAT-T doesn't appear to work), I use VPN Azure to connect.

Connecting from a Windows client (version 9760), everything works beautifully, including UDP acceleration.

When I try to connect using a Linux-based client (5.02 build 5180 - 4.xx versions don't work, unfortunately) on the same network as my windows PC, with the exact same config file, however, I end up with a TCP connection (with 4 times the lagginess)... Weirdest of all, it shows that UDP acceleration is supported - just not active. Any suggestions how I could troubleshoot this?

Thanks!

Linux client status excerpt:

Code: Select all

Half Duplex TCP Connection Mode:No (Full Duplex Mode)
VoIP / QoS Function:Enabled
Number of TCP Connections:4
Maximum Number of TCP Connections:4
Encryption:Enabled (Algorithm: AES128-SHA)
Use of Compression:No (No Compression)
Physical Underlay Protocol:TCP/IP via VPN Azure (IPv4)
UDP Acceleration is Supported:Yes
UDP Acceleration is Active:No

Windows client status excerpt:

Code: Select all

Half Duplex TCP Connection Mode:No (Full Duplex Mode)
VoIP / QoS Function:Enabled
Number of TCP Connections:2
Maximum Number of TCP Connections:2
Encryption:Enabled (Algorithm: RC4-MD5)
Use of Compression:No (No Compression)
Physical Underlay Protocol:TCP/IP via VPN Azure (IPv4)
IPv4 VPNAzure UDPAccel_Ver=2 ChachaPoly_OpenSSL UDPAccel_MSS=1309
UDP Acceleration is Supported:Yes
UDP Acceleration is Active:Yes

Posted: **Thu Dec 16, 2021 1:33 am**

Are windows and Linux clients in the same network? UDP acceleration does not work in all networks.

Posted: **Thu Dec 16, 2021 4:14 pm**

Unfortunately that's not it - both clients are on the same network...

Posted: **Thu Dec 16, 2021 4:34 pm**

Are you using the latest code from 5.02? If you are using some existing release, it's very likely there is some bug.

Posted: **Thu Dec 16, 2021 5:10 pm**

You also need to know that UDP acceleration turns active after 10 seconds of successful UDP keep alive. If there is some interrupt in the past 10 seconds, it's inactive.

Posted: **Mon Dec 20, 2021 8:17 pm**

The described behavior is with 4.38 server, and 5.02 build 5180 client (Github release June 2021). The client I'm unfortunately stuck with this particular release.
However, since it appears to be platform-dependent rather than version-dependent, I'm more inclined to think it's something off in how my client is set up otherwise (i.e. system-level interference in the UDP), rather than an actual bug. But without some options for how I could test UDP connectivity outside of Softether VPN, to see if it's really Softether specific, it's hard to tell. Is there some way for me to check connectivity/keepalive etc?

(On server-side, I did actually try to upgrade from 4.38 to the 5.02 release and very latest 5.02 nightly. This unfortunately breaks VPN Azure entirely for me, while suddenly allowing DynDNS+NAT-T to work. This one seems more like an actual bug to me and I opened an issue on GitHub for it).

SoftEther VPN User Forum

UDP accel. supported, but not active?

UDP accel. supported, but not active?

Re: UDP accel. supported, but not active?

Re: UDP accel. supported, but not active?

Re: UDP accel. supported, but not active?

Re: UDP accel. supported, but not active?

Re: UDP accel. supported, but not active?