I was thinking if i had RB1100AHx2 router, wich eth ports are best practise setup for routing local area network if i have two cables one is from ISP and the other to switch to network, i know that rb1100ahx2 has two switch groups with cpu’s but what about eth 11;12;13 ports?
witch of ports would you use for routing ? 11 12? or just any of first or second group?
what about backup line?
thanks for your answers 
Routing is done via the CPU so switch groups shouldn’t make any difference.
Switch groups are to create independent layer 2 network segments, which allow devices connected within the switch group to inter-communicate without going through the cpu/firewall, however you can also apply filtering within a switch group too, but that functionality is much less than the proper IP firewall.
Oh, mow it’s more clear, strange thing was for me that ports 11 12 13 aint assigned to any switch group, so i got lost here…