A method allowing for flexible modification of a data packet in a data network is presented. A data packet is parsed based on one or more attributes and sent to a buffer memory and a user modifiable lookup table. Using extracted packet data, information required to modify the data packet as desired is located in the lookup table and forwarded to a packet modification engine. Within the packet modification engine, a novel rewrite constructor module generates unique packet rewrite information based on the information forwarded from the lookup table and one or more additional inputs. This unique packet rewrite information is forwarded to a packet rewrite engine, wherein the packet rewrite engine modifies the data packet accordingly.