This is highly determined by snooping configuration restrictions; where by on certain swithches, you may find that DHCP commands are not available. That is, if such are commands are entered, the switch gives an error message, hence configuration not applied. best way to go over this also is to look at the DHCP snooping configuration guidelines.

For educational purposes, please view this link.

http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfdhcp.html

Thanks for the reference Erias..