PowerConnect 5548 DNS issue

Hi All,

I have enabled the DHCP function in my 5548 switch and set the DNS IP. However, when the client connect to the switch, it can get the IP, network mask and gateway properly but can't get the DNS IP which I have set in the switch. May I know how I can solve this issue? 

console (config)# ip domain lookup 
console(config)# ip name-server 202.175.3.3

Thanks,

Jacky