RT-AC68U disconnects but reconnects immediately with an action like ping

[gurc4n]

Hello network gurus,
I have a Huawei B535-232 modem in bridge mode and RT-AC68U in router mode.
Internet disconnects like 30 minutes later after the setup. If I log in to the Asus management menu and make a ping to google.com, it immediately reconnects.

Is there a way to make keep alive packages on Automatic IP mode bridge connections?

What can I do to overcome this issue?

 

[ColinTaylor]

What firmware version?

It should already be sending period checks to the internet. But additionally you can configure:

Administration - System > Network Monitoring > Ping

 

[gurc4n]

It is on the latest Merlin.
I set the modem back to router mode and set the Asus to access point. Since then everything is fine. But I want to use Asus as the router.