I have a small computer running ElementaryOS 5.1 Hera with an issue I am not yet able to explain. The IPv4 network connection stops working after a certain amount of operation, about an hour or so. When the system starts up, the settings panel for my wired ethernet connection looks fine and connection works well. Shown on screenshot#1.
Then, after some time of operation, what I notice is that all downloads/seeds in Transmission are stalled, or opening an SSH or SFTP connection to another computer on my home network fails, etc. At that point the settings panel of the wired ethernet connection no longer shows the values of the IPv4 address, subnet mask, and router fields. IPv6 address is still there though. This is shown on screenshot#2. In the top-right corner of this settings panel, there is a little slider button. All I need to do is slide it to the OFF position, and immediately slide it back to the ON position, and the wired ethernet interface once again has IPv4 address, subnet mask, router, and my connection works fine. Looks like a DHCP renew.
I was wondering if this is related to the Lease Time of my DHCP server (the connection box provided by my ISP - has a web management interface). But other computers on the same network never behave this way. There is a Mac laptop running macOS, another laptop running Windows, and a desktop PC running FreeBSD. Only the mini computer with ElementaryOS drops its IPv4 settings, and only after an hour or so, the others always work fine for as long as we keep them on. Also, the mini computer does not drop its IPv4 settings when a different operating system is used on it (tried with FreeBSD and Windows).
I am not very familiar with ElementaryOS, particularly about its internal workings and most of the Linux-specific things in it. I have way more experience with the BSDs. So this may just be something very trivial for an average Linux guy.
Question: What can I do to stop the IPv4 configuration vanishing from the Hera machine? Or what can I do to automatically get this refreshed when it expired?
Any suggestion or pointer is much appreciated. And I do not mind to RTFM once I am pointed to the appropriate pages.