Non-Terminal DNS Name Redirection (RFC2672)
Original Publication Date: 1999-Aug-01
Included in the Prior Art Database: 2000-Sep-13
Internet Society Requests For Comment (RFCs)
This document defines a new DNS Resource Record called "DNAME", which provides the capability to map an entire subtree of the DNS name space to another domain. It differs from the CNAME record which maps a single node of the name space.
Network Working Group M. Crawford
Request for Comments: 2672 Fermilab
Category: Standards Track August 1999
Non-Terminal DNS Name Redirection
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document defines a new DNS Resource Record called "DNAME", which
provides the capability to map an entire subtree of the DNS name
space to another domain. It differs from the CNAME record which maps
a single node of the name space.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [KWORD].
This Resource Record and its processing rules were conceived as a
solution to the problem of maintaining address-to-name mappings in a
context of network renumbering. Without the DNAME mechanism, an
authoritative DNS server for the address-to-name mappings of some
network must be reconfigured when that network is renumbered. With
DNAME, the zone can be constructed so that it needs no modification
when renumbered. DNAME can also be useful in other situations, such
as when an organizational unit is renamed.
3. The DNAME Resource Record
The DNAME RR has mnemonic DNAME and type code 39 (decimal).
DNAME has the following format:
The format is not class-sensitive. All fields are required. The
The DNAME RR causes type NS additional section processing.
The effect of the DNAME record is the substitution of the record's
descendants" limitation governs the use of DNAMEs in a zone file:
If a DNAME RR is present at a node N, there may be other data at N
(except a CNAME or another DNAME), but there MUST be no data at
any descendant of N. This restriction applies only to records of
the same class as the DNAME record.
This rule assures predictable results when a DNAME record is cached
by a server which is not authoritative for the record's zone. It
MUST be enforced when authoritative zone data is loaded. Together
with the rules for DNS zone authority [DNSCLR] it implies that DNAME
and NS records can only coexist at the top of a zone which has only
The compression scheme of [DNSIS] MUST NOT be applied to the RDATA
portion of a DNAME record unless the sending...