The Everything Feed - All Packet Pushers Pods IPB186: An Inside Look at RFC 9872 for Discovering v6 Prefixes
Oct 23, 2025
Explore the ins and outs of RFC 9872, which tackles NAT64 prefix discovery for IPv4-to-V6 translation. Co-author Nick Buralgio reveals the flaws in previous RFC 7050 and how it sparked the need for modern operational guidance. Learn why PREF64 via router advertisements is becoming the go-to method, offering better management and scaling than DNS64. Discover practical tips for network operators on evaluating their options and the motivations behind promoting PREF64 adoption.
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Pref64 As The Preferred Discovery Mechanism
- RFC 9872 recommends using RFC 8781 (Pref64 RA) instead of RFC 7050 (DNS64) when possible.
- The document is informational operational guidance to encourage Pref64 adoption and modernize deployment practices.
Assess Support And Use Fallbacks
- Assess whether your hosts and network gear support RFC 8781 before choosing a discovery method.
- If clients or routers lack support, run RFC 7050 concurrently as a fallback during transition.
Hotel Bar Sparks A Fast RFC
- RFC 9872 began from a hotel-bar conversation among the authors to prefer Pref64 over 7050.
- They moved the idea through the IETF quickly and published the RFC within about 13 months.