| Internet-Draft | DNS64 flag for DNS RA Option | August 2025 |
| Ma & Xie | Expires 2 March 2026 | [Page] |
This document defines a new flag in the DNS RA Option to advertise the DNS64 functionality. This extension enables automatic configuration of DNS64 resolution, improving deployability in IPv6 transition scenarios.¶
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DNS Extensions for Network Address Translation from IPv6 clients to IPv4 servers (DNS64)[RFC6147] is a widely deployed mechanism for IPv6-only networks requiring access to IPv4-only services. [I-D.ma-v6ops-5g-ipv6only]introduce the reasons for using RA to deliver DNS64 address configuration. This document defines a new flag in the DNS RA option[RFC8106] to communicate DNS64 server address to hosts.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14[RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
Based on [RFC8106], this specification introduces a 'T' flag bit allocated in the leftmost bit of the Reserved field to signal the presence of DNS64 server addresses in the option payload. Figure 1 shows the format of the DNS64 option.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length |T| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | DNS64 Server Address(es) (128-bit IPv6) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1:DNS64 RA Option format¶
Fields:¶
This memo does not introduce any new security problems. Considerations are described in Section 7 in [RFC8106]¶
This document requests allocation for the Flag T.¶
The comments and suggestions of the following are gratefully acknowledged:¶