On an entirely different point, I would like to start a separate thread about the best way to represent IPv6 numbers in Perl. I have the following thoughts. Possible ways may be: (1) Using a 128 element binary array, and writing all the binary maths yourself to manipulate that. (2) Using a 4 element array storing four hex characters from 0 to F. Probably far slower than the above method, but smaller for storing many IPs. I know that Perl can natively think in hex, so maybe it would be faster than I think. (3) Having a complex structure, where the IP number is stored in parts - the top /48 (in any of several formats), with variable structure subnets underneath that. Could be tricky for the maths, if the variable bits are badly thought out. (4) Storing four "IPv4-esque" decimal strings in an array, or as part of an object. Then do the maths on each of those separately. Probably fast. (5) Storing a single parant /48 object (in any format) and have child objects with only the bottom parts of the IP to worry about. I wonder how that would work. -------- When I have gone away and read more of Mastering Algorithms with Perl, I will come back and maybe make some more comments. Just as a disclaimer - I am in no way making any comments on Manuel's already excellent libraries. I have already spoken to him about them, and would not want to appear to "go behind his back". This is an entirely intellectual exercise only. In fact, I would very much like to see Manuel post his own thoughts and real world experiences on the subject (of which I have none). I wish every one well, Guy -- Guy Vegoda \ guy@vegoda.org *Please do not send html* NIC: GUY-RIPE \ guy@cryptography.org.uk *attachments* Unix, Linux Hobbyist \ +44(0)20 7961 8318 (work) www.thenakedfrenchman.com \ +44(0)958 469 532 (cell)