I am currently blocking the private scopes via blackhole routes.
I just found out our ISP (Frontier FIOS) is routing some of the private scopes.
I am wondering if there is a correct way to implement these on a Mikrotik router.
The correct way is to contact them and tell them that their configuration is incorrect…
(not for all the blocks in rfc3330 of course, but only those that are supposed to be unroutable,
including the blocks from rfc1918)