Intermittent access problem to Softether server

[thenewone]

Hi all,
long term reader (and user) but first-time poster.
Sorry for the lenghtly post I am getting wits end, as most of the time (but not always) I have a connection error1, no access to the Softether server :-(
I am running Softether on my home server (windows 11) since probably five years with the same configuration.
Access is used occasionally when traveling hence I only some two weeks ago that I cant access anymore via my laptop.
Last successful login was in January, now I get usually an error code 1 :-(

When playing around with settings I tried:
• Turning off windows firewall
• Turning on "VPN over ICMP/DNS"
• Enabling Virtual NAT and DHCP

All with no success.
T
hen I found the new softether release a few days ago, installed on both laptop and server, and, voila, connection worked!

But not for long and the same problem started , error code 1 again
What I found by try and error is the following:
• As soon as I re-install softether on the server over the existing installation (it keeps the config intact) it works again for a certain amount of time (may be a few hours)
• I am running docker on the server as well. It seems to work a bit longer when I turn docker off, but as soon as activate docker the error code 1 comes back immediately

I am by no means a very network savvy person but after not having many issues with it for several years I am somehow thinking that some Windows updates might cause the use.
I had a similar problem with Windows in the past but I was able to recover via a recovery point.
I stopped Windows updates (not a good solution either) until there was a compatible update again months later.
Unfortunately, this time I don’t have an early enough recovery point to go back to the last known working state easily.

But nevertheless, after searching high and low I could not find a solution or somebody who had a similar problem.
Does anybody have any suggestions about what I could try?

BTW: For testing I installed Tailscale and is connecting always successfully to the same machine without issues, but I would prefer to stick with Softether

Cheers
Mike

[solo]

If you rely on NAT-T, intermittent connections are expected. It's somewhat similar to viewtopic.php?f=7&t=69614
As for Tailscale, it will always work in gateway/relay mode, just like SE VPN Azure.

[thenewone]

Thanks for the quick response :-)

NAT/T is disabled on the client.
Would I have to change something on the server sided as well?

And with the current settings the connection was rock-solid for literally years???
And why does it work for a few hours after a new install?

Any suggestion where I could look further?

Cheers
Mike

[solo]

No worries ;-)

For a test please check if it's better or resolved on your VPN Azure address.

[thenewone]

Well, that makes an difference!
It works for both with or without NAT/T disabled, butboy o boy, that azure VPN connection is slow :-(

With NAT/T is disabled it is a bit better but I still dont even get a throughput of 1M, and I am using a 5G connection for the client.
Is there any option to optimize the speed? With this throughput it is a pain to use

The old connection over softether.net (if it is working) is ways faster

Cheers
Mike

[solo]

It was only a diagnostic test, not a permanent solution. Now we know that your SE setup and its OS are fine. The original problem is with your router, ISP or VM host (if applicable).

[thenewone]

Thanks for helping, as said I am not the most savvy network person. ;-)
Considering that it is working for a while when I reinstall the softether server with the same config, (and it was working some three months ago) what would be your suggestion where to look at?
Router has forwarded the port range for softether to the server IP but no config been cahned since I installed softhether years ago
Cheers
Mike

[solo]

Let's confirm the diagnosis with test #2
- create a hub w/o a bridge nor SecureNAT
- connect to it from a LAN PC using your server's LAN address
- ignore/close the DHCP dialog box as we're only interested in connectivity status

?

[thenewone]

ok, I did install a second virtual hub for testing and a second VPN connection in the client software
Secure NAT disabled on both virtual hub and client
Laptop was connected to the sma LAN as the server
Same result, no connection if I am using *.softether.net as hostname, it works if I am using using *.azure.net :-(
Does that mean I have an issue with my ISP?
Cheers
Mike

[solo]

But "connect to it from a LAN PC using your server's LAN address" is a private IP, like 192.168.x.x...

[thenewone]

Correct that would be a local IP address for both client and server, but isn't the VPN connection going via the Internet?
Maybe I have the wrong understanding but I would have thought that the VPN connection, even if client and server on the same LAN would go via an Internet tunnel from the LAN and back to the LAN?
As said I am not a network guru at all so appreciate if you could advise what can conclude from the test.
Cheers
Mike

[solo]

If it works on LAN, you can focus on fixing your router or ISP. C'mon mate, it's taking too long ;-)

[thenewone]

But it does not work on LAN!
Same result like if I am going over an external Internet connection:
no connection if I am using *.softether.net as hostname, it works (but slow) if I am using using *.azure.net.
Any other suggestions?

[solo]

Temporarily disable the server's firewall, then start your LAN VPN and post AS CODE the output of:

Code: Select all

	VPN server:
netstat -r
ipconfig /all
netstat -anbp tcp
netsh advfirewall show allprofiles state

	VPN client:
netstat -r
ipconfig /all
ping [SE server's LAN address]
tracert -d [SE server's LAN address]
"C:\Program Files\SoftEther VPN Client\vpncmd.exe" localhost /client /cmd AccountStatusGet [name of the LAN connection]

[thenewone]

Go figure, it works now with an acceptable through put.
The only thing I changed (for some other reason) was allowing IPv6 on the LAN.
I assume further trouble shooting will not make sense if there is no problem, at least for the moment.
I will report back in case the problem starts again.

Thanks heaps for your help so far

Cheers
Mike