Hi.

My ISP assigns me two blocks of public IP's in different subnets - lets say 1.1.1.0/24 with GW 1.1.1.1 and 222.222.222.0/24 with GW 222.222.222.1. Both arrive on a single interface.

On the LAN side I am NATing to 192.168.5.x

I need to ensure routing works on both WAN IP ranges. I am not trying to load balance - I just want traffic sent to a specific IP to receive a reply from the same IP, and not from the default gateway route.

I see posts like http://forum.mikrotik.com/viewtopic.php?t=46706 which suggest it can be done if each subnet was presented to a separate interface, but this is not the case here.

There is an SMTP server on the 222.222.222.x side that needs to be quite separate to the web servers on the 1.1.1.x side of things.

I am using DSTNAT to present the web servers to the world and SRCNAT to allow traffic out on the correct IP.

Is there anything else I need to do in this case? I see references to mangle marking packets by interface then creating IP Route rules to route traffic - and marking the routes to match. Is this correct in this scenario or does it not matter with a single physical interface involved?