The Smart PING of the Micro Core now per defaults creates exactly the same type of packets that a plain command line ping does. This has the disadvantage of creating larger packets then neccessary - but has the advantage of being compatible with more firewalls. Some of those tend to regard ICMP ECHO REQUEST packets without payload as some bogus attack and drop them.
You can reenable PING packets without payout via a new global option for main.mk:
cmc_smartping_omit_payload = True
This is also available via WATO in the global settings of the Micro Core.