I have an edge router with NAT and OSPF, which uses a lot of CPU. I would like to be able to set up two routers, one for NAT and the other for OSPF. Since I'm a beginner at this, I would like to know if anyone has done this before and how they did it to avoid problems. Thanks in advance for your help!
Hi,
OSPF is used to propagate routes between routers.
Don't you need the proper routing table at the NATting device?
Thanks for pointing that out! My plan is to remove OSPF from the NAT device to save CPU, and instead use static routes (or a default route pointing to the inner OSPF router) so the NAT device still knows where to forward the return traffic. Do you think that approach would work well, or is there a better way to do it?
If you want to put static routes into a route table then you loose whole idea behind dynamic updates. The solution is properly designed OSPF + iBGP. When you change something somewhere then you have manualy update it at NAT device. Big no-no 
OSPF should be used just for links between routers to let iBGP makes it's job over the OSPF managed links. OSPF should propagate as small tables as it can using summarization. /routing/ospf - RouterOS - MikroTik Documentation
Many people do what you propose, in fact this is the recommended arrangement. Separating NAT and IGP functionality is generally a good idea. Lots of people go as far as turning off connection tracking on their routing devices.
You won't experience any trouble. You will of course have to manually inject the routes to/from the NAT device, but that's just life.
did you looked at Switch / L3HW ?
maybe you have L3HW capable device, then you could use L3HW fasttrack/NAT ?