Recently I got an email from a colleague at a sizable ISP. He said his executive vice president wanted to know whether it was safer to use 22.0.0.0/8 or 30.0.0.0/8 for additional RFC1918 address space. I have to say I was shocked. I thought maybe I didn’t understand him. I rewrote back,
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Some thoughts on IPv6 reverse DNS. Lee Howard was speaking in the Sunset4 working group at IETF 90. He mentioned something that got me thinking. I have often discussed in my talks problems in IPv6 that were unanticipated. A lot of these problems are unintended consequences of very large subnet sizes. Some problems are outlined in RFC 6583. Lee mentioned another interesting problem, reverse DNS. Best practice [RFC1033] says that every Internet-reachable host should have a name (per RFC 1912) that is recorded with a PTR record in the .arpa zone. It also says that the PTR and the A record must match.
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ARIN Advisory Council member, Cathy Aronson, is at IETF 90 in Toronto, Ontario, Canada this week. Follow along as she shares her findings with us on TeamARIN! Yesterday morning I attended the IEPG (Internet Engineering and Planning Group) meeting here at IETF 90. George Michaelson of APNIC gave an interesting presentation about Teredo (a tunneling technology that allows IPv6 capable hosts to use IPv6 over a IPv4 only connection). George’s slides are here. The great thing about his presentation is that he observed Microsoft doing exactly what they said they were going to do. They turned off their Teredo relays. It is clear in George’s graphs that the Microsoft Teredo relays have been turned off. The presentations about sunsetting Teredo are linked here:
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