I never tried it:https://supportforums.cisco.com/discussion/11593786/nat-udp-port-range-forwarding-howtobut as you could see may be some problems with udp.Easiest way insert only 2 lines in config: ip nat inside source static 192.168.200.100 interfac...

Could you post your config

Debug output could be redirected to syslog server logging trap debugginglogging my.syslog.server  

About problem of dropping connections with DHCP – its our (users) bug not IOSI found in your config line: ip nat inside source static 192.168.200.100 interface ATM0.1 All traffic is forwarded to your local server 192.168.200.100 including answers fro...