On the ethernet1 interface, I noticed UDP packets coming out every 1 second from 0.0.0.0:68 to 255.255.255.255:67 although I don’t have a DHCP client configured.
The ethernet1 port is connected to GPON ONT and used by the pppoe connection.
RouterOS 6.46.4.
What service sends these packets and how to disable it?
Hello Piotr
I have the exact same issue with my CRS-125 at the same ROS version. I have no DHCP-client setup on that router.
After having read other posts, II found that I have an “Alert” rule setup in my DHCP server. After disabling it, voilà! No more false requests.
So much trouble because I was playing around with MTCTCE. 
Hope this solves your issue.
Cheers!