1) This problem occurs for every firmware 1.0, 1.1, 1.2 and SDN v4 and v5 2) I have one L2TP VPN to the company and 2 PPTP to the remote sites. Both PPTP are barely used. This behaviour does occur to all of them. More VPN active more chance to occuring of the problem. I think that @shberge found the reason of problem - connection drop if VPN is reconnected - so more VPN, more reconnections. 3) VPN traffic was very low and it does not matter (same results with/without VPN traffic). Problem is also when I am copying through VPN some large files which takes more than hour. This also results in interruption of the file transfer. From my point of view is VPN really unstable. This does not occur if I am connected to VPN directly through computer (Windows 10 VPN manager).

  @Libik 

I'm not sure if it can help you but I have using a ping tool on linux, where using fping,

it can read a file with ip addresses and ping reguary remote site,

this has helped me a lot, ping to remote lan keeps the vpn tunnel open and does not go down due to inactivity.

then I use crontab to start fping. you start crontab with this command

crontab -e

then put in this line. (edit if you use anoter path or ping file)

@reboot sleep 10 && sudo fping -f /home/ubuntu/ping_hosts.txt -l -p 100000

then restart your liux server

this checks all remote site regualry and keeps the VPN tunnel open.

you need to create a file that you put the ip addresses on the remote site like this, I have named this file name like this ping_hosts.txt one ip then new line

192.168.1.1
192.168.2.1 

I have hudreds of VPN tunnels but Tp-link is the only one that ned this bad workaround to work, this is not 100% but muhc better .

More information about this tool

https://ostechnix.com/ping-multiple-hosts-linux/

Hello, ping wirh crontab does not help me. every 55 minutes L2TP VPN reconnects and this leads to interruption of internet connection. I have also tried to copy file from remote site using VPN and L2TP was also reconnected after 55 minutes. PPTP does not suffer from this. If I am connected to the same VPN using Windows 10 VPN client no reconnection.

  @Libik 

Do you have a solution to your problem or has Tp-Link ignored you as well? it does not seem that they are interested in solving VPN problems on what they call VPN router.

  @Libik 

Ok, you have at last progres  I have about 50-100 mail with support over 3 month and they steel not understand so I have for now giving up, if they cant find all this serios bugs they problably dont want to find it or have a serious test lab isue.

they have many more vpn bugs that I have not even bothered to mention so I hope they can find these on their own one time in the future.

I have just upgrade my Linux Controller to version V5.1.7 with the same bad behaviour:-(.

@shberge

Does standalone mode behave the same or it is working as expected?