Hello samso....
yes, as my screen captured and i used it several months ago and until now working fine.
again, when you want one local address as public one, at my first post should be work.
you must add public address as broadcase itself.
/ip add add address=a.b.c.22/32 interface=internet
and create any rules Network Address Translation:
/ip fi nat add chain=dstnat action=dst-nat to-addresses=192.168.2.251/32 to-ports=0-65535 dst-address=a.b.c.22/32
/ip fi nat add chain=srcnat action=src-nat scr-address=192.168.2.251/32 to-ports=0-65535 to-address=a.b.c.22/32
i think with this rules should be ok... 
and i hope will closed your problem
again, i don't have any problems about this.. sorry...!!!