How to Connect all Systems in a network

I have an 4 MBPS Lease Line connection & 16 MBPS Broad band connection. Using 48 port managed Cisco switch 10/100/1000 Base T.

I have asigned an IP to all system :

For lease Line = 192.168.2.1 - 192.168.2.254 series

For Broad Band = 192.168.1.1 - 192.168.1.254 series.

But still i am facing an issues like,

i. slow internet connection

ii. frequent internet disconnection