You could change the route target extended community attribute in the same way as the standard community attribute. However, setting extended community attributes through route maps applied to route redistribution, or to BGP neighbors, is not support...
use ip dhcp snooping for particular vlan that you want to filter.First enable it globallyip dhcp snoopingSecond add particular vlanip dhcp snooping vlan vlan_numberThe switch will ignore any dhcp request for all access ports for enabled vlan