Nat to other LAN using mikrotik routeros

Question

I have a mikrotik rb4011igs with following connections:

• WAN on port1

• Bridge with DHCP for lan on ports2-9

• Other LAN on port10 (I cant make any changes to this networks router, so cant change the default gateway for this LANs devices)

Now I want to be able to access the other LAN devices with their addresses from my LAN(other LANs devices dont need to access the mikrotiks LAN).

As far as I understand, I need to create some NAT rules with some kind of masquerading, but unfortunately I'm not sure what to do exactly.

Answer 1

You need to add a NAT rule when packets travel through your router to the foreign LAN you want to access, so that all packets appear to come from your router when accessing that LAN. You need to do this because since you have no control over the router on the other network you can't write a route back to your LAN.

IP - Firewall - NAT

Add rule

General Tab Chain: srcnat Out. Interface: ether10

Action Tab Action: masquerade

Make sure this new rule is above all other NAT rules.

Answer 2

You need add a nat rule when your outgoing interface is the WAN port (To allow access to internet). If want allow your LANs connect between them you need two access rule(the NAT rule is not required):

1. Allow from LAN1 to LAN2.
2. Allow from LAN2 to LAN1.

Note: Remember set your gateway to the mikrotik