Hi all,
I have an stupid question, but i want to know how i can set my routerboard as router in the same subnet of existing network:
I have a router that provide me a DHCP with 192.168.1.X address, i want to connect the ether1 of my mikrotik of this network, set an static ip in the same class and connect the client to my mikrotik to relay the same DHCP of first router.
Sort of extension of network, i don’t know if you understood what i want to do…
Thank You! 
So you don’t want to route but to bridge… Enslave all interfaces into one common bridge.
Sounds like you want a switch. The Mikrotik can be configured as such.
IP > Interface, go through ether2 - ether5, set master port to ether1.
IP > Bridge > Ports. Remove ether2 and add ether1 to bridge-local
IP > DHCP Server, delete the entry
IP > Address, delete the default 192.168.88.0 entry
IP > DHCP Client, edit entry. Set interface to bridge-local
IP > Firewall > NAT, delete the masquerade rule for ether1
Now your Mikrotik is a switch, and obtains an IP from the DHCP server so that you can still remote into it via IP.