The "best" way of storing things depends on what you want to do with them. On several levels even, from the low level storage (disks? RAID?) to high level issues like what kind of datastructure, or table structure.

split and join could do the task very well, or they are totally unsuitable. But that depends on how you are going to use the data. If you always want to return all IP numbers, and are never using them in a (database) join, then putting them in a string might work very well. If you need to search on IP number, or need them in a join, you need to do something else. Perhaps a one to many table, with two or three columns: first column is the name, second column is an IP number. You repeat the name for each IP number belonging to said name. You could use an optional third column with a sequence number.

-- Abigail