I am currently running a Mikrotik Cloud Core router that is connected to our ISP. Our ISP has given us a /29 of public addresses. I was planning to give one of those addresses to a server that we have but I found that one of our Routerboard2011s was attached to that address. So I looked at the conifguration to see if it had been assigned previously for management purposes. But inside the configuration there are no public IP addresses but the cloud core routes it to that Routerboard. There is no DHCP server or client setup on these routers. The only thing that I can think of that it could be getting that address is through OSPF but I am still scratching my head as to how.
Export the configs for both routers and post them here so that we can see what’s going on.
OSPF doesn’t assign addresses.
Look in the RB with that IP attached for Interfaces for pppoe, EoIP or any kind of tunnel; also any DHCP client attached to a VLAN or similar.