My RouterOS Configure Question

My RouterOS want to to configure such environment。
My RouterOS has 3 network cards。
The first network card makes the WAN Port (218.19.25.122/30,The gateway is 218.19.25.121) * the telecommunication provides *

The second network card makes fixed IP the route gateway, establishes
IP:61.142.58.193/28, such 61.142.58.192/28 section of IP passes
through 61.142.58.193 gateways to pass through the WAN Port route
again to the Internet. * The telecommunication provides other provides
section of IP*

The third network card makes the LAN Port, makes NAT using WAN
IP218.19.25.122/30, the under computer through connects in the LAN Port
sharing the Internet。

How do I dispose in RouterOS can use the second network card to make
the fixed IP section the route gateway,For example PC Config the IP address: 61.142.58.196/28, the gateway
Config: 61.142.58.193, Can on the Internet,The Internet also may connect this IP address。


Thanks!

What version of MT are you using?