...for local authentication i have cyberoam firewall
What do you mean by "authentication" from a firewall? What are you authenticating? And once again, are there any devices other than WiFi devices attached to the Mikrotik?
Please specify whether your Local network is running on a dhcp and if so you cannot run DHCP on the WIFI and the same time on the server on the local network.Otherwise make sure that you run it on the server only and just specify the scopes.