The invention relates to a method of routing or compressing packets destination address through an electronic routing or compressing device, the packets destination address being n bit packets and having address indicative of a desired destination, the address being classless, the routing device having at least a data base of prefix entries, each of which containing entries corresponding to a desired output data link, the method having the steps of: a) generating an address mask until an entry matching a masked address obtained by making an AND operation between the packets destination address and the address mask, is found in the data; the address mask having a number of bit equal to that of the packets destination address and having, starting from the most significant n-bit equal to 1 and the remaining i bit equal to 0, with 0<=u<=b.1, with the first generated mask having i=0 or i=1, b) if a match is found, stopping the generation of masked address and outputting the output data link corresponding to the match, c) if no match is found, outputting a message indicating that no output data link was found.