Try to be more specific with the question(s) and ask discrete questions which other users can easily answer in a minute or so.
In broad terms:
a) You need to masquerade traffic heading to the ISP from your various LAN segments
b) You control traffic among the LANs and to/from the ISP using the forwarding table in IP Firewall.
c) You should have a look at the Wiki entries concerning securing our router. e.g. : http://wiki.mikrotik.com/wiki/Securing_ ... rOs_Router
frankly i dont see how i could be more specific than that ..... i have a old puter/ turned router with 3 network cards .... one is currently being used for general internet access, i wanted to utilize the other 2 " idling " cards for network access for my servers & the other for wirrless hotspot
Try to be more specific as this for example
you currently have only 1 network and try to expand your network into 3 networks.
192.168.1.0/24 is currently your home network, you are trying to add 192.168.100.0/24 as server network and 192.168.2.0/24 as wifi network. you don't want host in the wifi network ease to access server network. You only need that server can server general purpose for wifi network as webserver, mail server or FTP server.
- Let's say you have configured 192.168.1.1 on eth0 as network gateway.
- you will configure the other networks on another network interface (eth1 and eth2).
- put 192.168.100.0/24 on eth1, and you can put 192.168.2.0/24 in eth2
- you can give 192.168.100.1 as IP Add of eth1 and 192.168.2.1 as IP Add of eth2
- add 2 action masquarade in ip->firewall->nat chain src-nat src address 192.168.100.0/24 and src address 192.168.2.0/24
- add action accept src address 192.168.2.0/24 and dst address 192.168.100.1/24 in ip->firewall->filter (specified ports you want to open on the server for user hotspot)
- add action drop src address 192.168.2.0/24 and dst address 192.168.100.1/24 in ip->firewall->filter (will drop other packet unspecified on the firewall rule above)
- if you need further complex configuration for network security, bandwidth management, I suggest you to read the wiki first then floor it in here when you don't really understand what wiki/manual have told you.
This question should have very simple answer but you made it too ambiguous, so it became more complex and spend more time for professionals to explain it to you. Hope this answer can ring the bell on your head.