I've configured all 3 Mikrotik boxes on our network to sniff DNS traffic and forward it a host running tcpdump.
The requests for cloud.mikrotik.com appear directly on the PPPoE interface of that's our link to the external world. No requests at all from the two other Mikrotik routers acting as bridges on the internal network.
The requests go not only to the configured DNS provider but also to Google's public DNS. The router is not configured to use Mikrotik's public DNS.
/ip dns set allow-remote-requests=yes servers=208.67.222.222,208.67.222.220
And there are firewall rules to direct internal DNS requests to the DNS provider:
/ip firewall nat
add action=redirect chain=dstnat dst-port=53 in-interface=bridge protocol=tcp
add action=redirect chain=dstnat dst-port=53 in-interface=bridge protocol=udp
There is also a static DNS cache entry for cloud.mikrotik.com:
/ip dns static
add address=10.0.0.1 name=router
add address=81.198.87.240 comment="The repeating router address lookup." name=cloud.mikrotik.com ttl=1w
The requests happen at much shorter intervals than the 60 seconds advertised on
https://wiki.mikrotik.com/wiki/Manual:IP/Cloud
46725 42264.738922545 A.B.C.D → 208.67.222.222 DNS 125 Standard query 0x8ed0 A cloud.mikrotik.com
46726 42264.752259820 208.67.222.222 → A.B.C.D DNS 141 Standard query response 0x8ed0 A cloud.mikrotik.com A 81.198.87.240
46730 42282.798276192 A.B.C.D → 208.67.222.220 DNS 125 Standard query 0x93e4 A cloud.mikrotik.com
46731 42282.811413416 208.67.222.220 → A.B.C.D DNS 141 Standard query response 0x93e4 A cloud.mikrotik.com A 81.198.87.240
46732 42282.891949252 A.B.C.D → 8.8.8.8 DNS 125 Standard query 0xf123 A cloud.mikrotik.com
46733 42282.904804655 8.8.8.8 → A.B.C.D DNS 141 Standard query response 0xf123 A cloud.mikrotik.com A 81.198.87.240
And this is a feature that the user has turned off per Mikrotik's wiki:
/ip cloud> print
ddns-enabled: no
update-time: no
public-address: 93.89.129.17
status: updated
Naively, this looks broken. I manually forced a cloud update yesterday to see if this would quiet this feature. No joy.
Thanks