Nat

For each public IP create an address:

/ip address

add address=123.123.123.2/29 comment="IP 1" interface=ether1

Then create the NAT for each public IP. First create entries for allowing the traffic:

/ip firewall nat

add action=src-nat chain=srcnat comment="Server 1" src-address=192.168.1.2 to-addresses=123.123.123.2

add action=dst-nat chain=dstnat comment="Server 1" dst-address=123.123.123.2 to-addresses=192.168.1.2

And then you can create the rules for port forwarding:

/ip firewall nat

add chain=dstnat action=dst-nat dst-address=123.123.123.2 to-addresses=192.168.1.2 protocol=6 src-port=80 dst-port=80