It might just be my less than stellar understanding of networks, but I find it odd that the arp command on my mikrotik router shows, besides all my home devices connected to the bridge interface, connections from public ip's (usually starting with 192, somewhere from Canada and US) on the ether1 interface. On the ether1 interface there is my ISP router, which I use as a "modem". Was it my router that initiated these connections? What for? Are these ip's related to the ddns service or something? The whois command isn't helpful.

thanks

Does the output of /ip arp show also any MAC addresses associated to those IP addresses? If not, it may be just a wrong mask in the IP configuration of your Mikrotik's WAN interface, making it think that part (or all) of the 192.x.x.x range is in its connected subnet. If yes, and if the ISP's modem supports the "arp proxy" functionality, it may answer with its own MAC address to Mikrotik's ARP requests for these IPs; in this scenario, the same MAC address (of the ISP's modem) is shown for all those IPs.

You were right.
/ip arp did not show any mac address for this strange ip's and, for some reason, the netmask on the mikrotik wan was 255.0.0.0 (ISP router LAN is 192.168.1.0)
Changed it to 255.255.255.0 and have not yet seen any strange ip show up.
Thanks!

192.168.1.0 is, I guess, now in the "network" field associated to the address; what is after the / in the "address" field itself?

192.168.1.0 is, I guess, now in the "network" field associated to the address; what is after the / in the "address" field itself?

Sorry, I don't know what I was thinking when I wrote the previous post. I just edited it.
Thanks for your help!