Just a side comment. Depending on the purpose and expected lifetime of the application, you might have to deal with IPv6 addresses (http://en.wikipedia.org/wiki/Ipv6). In that case, you'd have to consider larger data types. If you wanted to stick to built-in types, uniqueidentifier could be an option (not very human readable, but atomic)-or you could go for binary(16) (or maybe varbinary(16) thinking also of ipv4) as implied by earlier post.