In order to have only relevant things in the log I un-ticked these two items according to Haga_Nova, and now it stopped.

Hi Clive_A, I have tried but not found any settings regarding Logs. Can you explain, please? Regards Borje

I use the ER605 to connect to my internet provider Telia via fiber and Dynamic IP. My log is alwas full (999+) as the router updates WAN IP every 10 minute! "WAN: DHCP client lease expired. Began...