Bug 42349 - DNS round robin solution using CNAME is against RFC
Summary: DNS round robin solution using CNAME is against RFC
Status: RESOLVED DUPLICATE of bug 23501
Alias: None
Product: Apache httpd-2
Classification: Unclassified
Component: Documentation (show other bugs)
Version: 2.5-HEAD
Hardware: Other other
: P2 normal (vote)
Target Milestone: ---
Assignee: HTTP Server Documentation List
Depends on:
Reported: 2007-05-07 22:30 UTC by Tarragon Allen
Modified: 2007-07-04 23:44 UTC (History)
0 users

for trunk (1.10 KB, patch)
2007-06-13 23:25 UTC, Takashi Sato
Details | Diff
for trunk (1.21 KB, patch)
2007-06-13 23:36 UTC, Takashi Sato
Details | Diff

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Description Tarragon Allen 2007-05-07 22:30:28 UTC
The Load Balancing solution 1 "DNS Round-Robin" as detailed here:


... is against RFC 2181, which states:

10.1. CNAME resource records

   The DNS CNAME ("canonical name") record exists to provide the
   canonical name associated with an alias name.  There may be only one
   such canonical name for any one alias.  That name should generally be
   a name that exists elsewhere in the DNS, though there are some rare
   applications for aliases with the accompanying canonical name
   undefined in the DNS.  An alias name (label of a CNAME record) may,
   if DNSSEC is in use, have SIG, NXT, and KEY RRs, but may have no
   other data.  That is, for any label in the DNS (any domain name)
   exactly one of the following is true:

     + one CNAME record exists, optionally accompanied by SIG, NXT, and
       KEY RRs,
     + one or more records exist, none being CNAME records,
     + the name exists, but has no associated RRs of any type,
     + the name does not exist at all.

Note the section that says "one" CNAME record, which means "not more than one".

From what I've been able to determine, there was multiple CNAME support in BIND
4.x, however this was phased out (but still supported) in BIND 8.x, and has been
completely removed from BIND 9.1+. Other name services may or may not support
multiple CNAME records, however it is not a reliable method of load balancing
and should not be given as such in the documentation. At the very least the
documentation should point out that this feature may not (and is unlikely to) be
supported by most DNS systems.
Comment 1 Takashi Sato 2007-06-13 23:25:27 UTC
Created attachment 20342 [details]
for trunk
Comment 2 Takashi Sato 2007-06-13 23:36:06 UTC
Created attachment 20343 [details]
for trunk

There's no www6
Comment 3 Takashi Sato 2007-07-04 23:44:29 UTC

*** This bug has been marked as a duplicate of 23501 ***