Not working ipsec/L2TP Setting

[Near]

Hello. I created a local bridge connection for clients to my server, meaning not using SecureNAT but LocalBridge. The router, TV, and computers connect stably and receive DHCP addresses, but there are issues with Android devices.

First, I enabled the necessary flags to allow Android to connect using the built-in Android client (screenshot attached). However, it does not connect. I used the Exсdev SoftEther application, which attempts to connect but fails. In the server logs, I reviewed the logs and found the following regarding the user "poner" (the one I specified for the Android connection):

In the provided logs, several points regarding the connection of the user "poner" and possible issues can be highlighted:

Successful Authentication:
The user "poner" successfully authenticated several times, indicating the correctness of the credentials and the proper functioning of the authentication mechanism.

Session Creation:
Each connection created a new session (e.g., "SID-PONER-4", "SID-PONER-5", "SID-PONER-9"), indicating that the user could initiate a connection to the VPN server.

Session Termination:
All sessions ended with the message "The VPN session has been deleted." This may indicate several possible reasons:
Administrator Disconnected the Session: If the administrator manages connections, they might have disconnected sessions, which is a normal practice.
Connection Issues: If the connection from the client to the VPN server was interrupted, this could be due to network problems or an unstable internet connection.

No Data:
The statistics for each session show that the total outgoing and incoming data is 0 bytes. This may indicate that the sessions did not establish active data exchange before being terminated.

Connection Errors:
The logs also contain entries indicating that some connections (e.g., "CID-5", "CID-10", "CID-15", "CID-20", "CID-22") were terminated with the reason "A client which is non-SoftEther VPN software has connected to the port." (code 5). This indicates that clients attempting to connect were not SoftEther VPN clients, which may suggest a configuration error or incorrect use of client software.

Additionally, the connection is being terminated for some reason, even though I have not explicitly prohibited it. The error "A client which is non-SoftEther VPN software has connected to the port" is also occurring.

I have written a series of iptables commands to ensure that the Local Bridge works; could this be related to the issues with Android connectivity? Here are the iptables commands:

bash

# Assign the value of the variable YOUREXTERNALIP

YOUREXTERNALIP=$(ifconfig ens3 | grep 'inet ' | awk '{print $2}')


# Configure SNAT for VPN traffic

sudo iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o ens3 -j SNAT --to-source $YOUREXTERNALIP


# Allow incoming traffic related to established connections

sudo iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


# Allow outgoing traffic

sudo iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


# Allow new traffic from the VPN network

sudo iptables -A INPUT -s 10.8.0.0/24 -m state --state NEW -j ACCEPT

sudo iptables -A OUTPUT -s 10.8.0.0/24 -m state --state NEW -j ACCEPT

sudo iptables -A FORWARD -s 10.8.0.0/24 -m state --state NEW -j ACCEPT


# Allow forwarding of traffic

sudo iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

Do I need to add anything else to these rules?

[Near]

I forgot to mention the log file I attached. It's also in the post

[solo]

Your "Android 15" has no L2TP support viewtopic.php?f=7&t=67903