/ip firewall filter
add chain=forward src-address=178.10.10.90 dst-address=10.88.88.100 action=accept comment="Allow 178.10.10.90 to 10.88.88.100"
add chain=forward src-address=178.10.10.90 dst-address=10.88.88.0/24 action=drop comment="Drop rest of 10.88.88.0/24 for 178.10.10.90"
add chain=forward src-address=178.10.10.0/24 dst-address=10.88.88.0/24 action=accept