Config MK for Network with Valid and Private IP Clients

Good Afternoon,
I'm having trouble setting up my network and would like your help.
Below is the current scenario (already running) and the new scenario (deploying MK)

Current Scenario (example) (already in operation):
ISP: 189.19.66.240/28
Gateway: 189.19.66.254

ISP router (189.19.66.254)
==>
Linux CPU (I can not access or restart due to an unsuccessful update)
NIC1 WAN - 189.19.66.241 (Connected to Router ISP)
NIC2 LAN - 10.0.0.2/16 (Connected Switch - customers - internal network)
==>
Client 1: 10.0.4.5/16 gateway 10.0.0.2
Client 2: 189.19.66.242/28 Gateway 189.19.66.254 - ping 189.19.66.254 OK and Navigation OK

The above scenario is already operational and has been run by the previous coach, but as I have no access to the machine to check and try to unravel the settings and do not know much of iptables / route want to remove and install a CPU mikrotik but I'm having difficulties in adapting mikrotik.

New Scenario (With Mikrotik):
MK - RB750
ETH1 = 189.19.66.241/28 --- Connected to router WAN ISP
ETH2 = Reserved
Eth3 = 10.0.0.2/16 - LAN - Connected to Switch Customers
ETH4 = Slave-eth3
ETH5 = Slave-eth3

ip -> Firewall --> Nat --> print
0 ;;; default configuration
chain=srcnat action=masquerade to-addresses=0.0.0.0 out-interface=ETH1
ip -> route --> print
0 A S 0.0.0.0/0 189.19.66.254 1
1 ADC 10.0.0.0/16 10.0.0.2 ETH3 0
2 ADC 189.19.66.240/28 190.19.66.241 ETH1 0



Client 1: 10.0.4.5/16 ----> Navigation OK
Client 2: 189.19.66.242/28 ----> No Navigation without ping 189.19.66.254 (ISP Router)

How to configure the MK to make it operate as Linux is already running? Both clients with Public IP and those who have Private IP navigate normally

I found some printed here the previous coach and has the following information (may be useful):
/ Etc / rc.d / rc.firewall

Open doors Validates Network

iptables -A INPUT -p tcp -s 0.0.0.0/0.0.0.0 -d 189.19.66.242 -j ACCEPT
iptables -A INPUT -p udp -s 0.0.0.0/0.0.0.0 -d 189.19.66.242 -j ACCEPT

/ Etc / rc.d / rc.rotas
#! / Bin / bash

Enabling routes to proxy

route add –host 189.19.66.242 dev eth1

Thank you in advance for all the help.

***Translator using google trans...