I am recently configured a cisco router 2811 for internet access to lan user. This router have two lan port. I port i configure for wan connection we have a lease line connection and other port i configure for dhcp lan connection to the user in LAN. i give opne dns to name server in cisco router and also in dhcp. Things going well but some user getting ip from dhcp but change the dns address to google. after chaning the dns to google they can access the restrict website. i want to route all the dns request to my cisco router name server. please provide the solution and i am beginer user to cisco routers.
I attach the my cisco rotuer configuration as attachement.