as i'm rolling v6 into my world, i'm not sure which way to go with reverse dns conventions. for forward i'm doing things like: foo.example.com a 1.1.1.1 foo.example.com aaaa 1000::1.1.1.1 foo.v4.example.com a 1.1.1.1 foo.v6.example.com aaaa 1000::1.1.1.1 so i can use a foo.v4/v6 hostname if i need to specify transit behavior. but for reverse i'm not sure if i want to map it like: 1.1.1.1.in-addr.arpa ptr foo.example.com. 1.0.1.0.1.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.ip6.arpa ptr foo.example.com or: 1.1.1.1.in-addr.arpa ptr foo.v4.example.com. 1.0.1.0.1.0.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1.ip6.arpa ptr foo.v6.example.com being able to just use foo.example.com for authentication purposes (sendmail, nfs, etc) is nice. but also knowing when incoming is v4 or v6 by just looking at the dns lookup (for tools that do reverse lookup for you) is also nice. what are you doing? which way makes more sense to you?