Posts By: Cathy Arsonson

To Squat or not to Squat?

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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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IETF 90 Part 2: IPv6 reverse DNS

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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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