debian - Delay in Internet connection when starting / stopping OpenVPN

Question

I have an OpenVPN server which is always running in the cloud, I can connect to it using an .ovpn configuration file from a client.

This client is a Debian OS and goes to the Internet via a Modem connection (SIM). Moreover, the client is executing a Java application which is connecting to an MQTT server via Eclipse Paho library.

When I start / stop the VPN service on the client, I notice (in the logs of the Java application) a significant delay in the MQTT reconnection (of the order of few minutes). What happens is that the MQTT connection drops, then there is a delay of 2 / 3 minutes, then again a restart. I have also a significant delay in executing PING on the client just after starting / stopping the VPN (for example, ping google.com takes at least 5 seconds to give the first response).

Problem is that my MQTT connection needs to send data about every minute, so the reconnection delay is actually impacting the correct functioning of the Java application.

I'd like to get some insight in the problems that might arise with this configuration and some help on where to find info & troubleshoot the problem.

Please ask if you need more details.

Thanks in advance.

Answer 1

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