Question about interface loopback + NAT

RouterOS General
1

Hi,

I work for a French small ISP.
I want to replace my CE Router from Cisco to Mikrotik.

Here you can see how we work today.
I tried 3 days to found how to nat the trafic from eth1 to eth0 using the loopback interface adddress.

If someone know how to do that, thank you in advance.

Cisco Config :

policy-map Global_C2E
 class class-default
  set cos 2
!
interface Loopback1500
 description PUBLIC_IP
 ip address 185.71.35.23 255.255.255.255
!
interface FastEthernet0/0
 description Fa(0/0) to Backbone
 mtu 1600
 no ip address
 speed 100
 full-duplex
!
interface FastEthernet0/0.2900
 description Fa(0/0.2900) to FR-MPL02-RTR001
 mtu 1600
 encapsulation dot1Q 2900
 ip address 10.10.10.254 255.255.255.0
 ip nat outside
 ip virtual-reassembly
 no cdp enable
 service-policy output Global_C2E
!
interface FastEthernet0/1
 description Fa(0/1) to LAN_CLIENT
 ip address 192.168.0.254 255.255.255.0
 ip nat inside
 ip virtual-reassembly
 duplex auto
 speed auto
!
ip nat inside source list 10 interface Loopback1500 overload
access-list 10 permit 192.168.0.0 0.0.255.255
ip route 0.0.0.0 0.0.0.0 10.10.10.254
2

You don’t have to send the traffic through a loopback address on a Mikrotik. Create a loopback interface using a bridge, add the public IP address to the loopback interface, use a srcnat rule specifying the public IP as the to-address:

/interface bridge
add name=loopback protocol-mode=none
/interface vlan
add interface=ether1 name=ether1.2900 vlan-id=2900
/ip address
add address=185.71.35.23 interface=loopback network=185.71.35.23
add address=10.10.10.254/24 interface=ether1.2900 network=10.10.10.0
add address=192.168.0.254/24 interface=ether2 network=192.168.0.0
/ip firewall nat
add action=src-nat chain=srcnat out-interface=ether1.2900 src-address=192.168.0.0/24 to-addresses=185.71.35.23
/ip route
add distance=1 gateway=10.10.10.1