Define a domains addresses sole in terms of another

Barry Margolin barmar at
Tue Jul 10 00:48:00 UTC 2007

In article <f6u9f2$1uva$1 at>,
 Stephane Bortzmeyer <bortzmeyer at> wrote:

> > webmail                          IN CNAME   www
> Forbidden, you cannot have a CNAME going to a CNAME.

Yes you can.  The RFC recommends against it for performance reasons, but 
doesn't prohibit it.  It even mentions that resolvers must follow CNAME 
chains, but may have limits on the number of CNAMEs that will be 
followed in order to avoid loops.

All the web sites that use DNS-based load balancing like Akamai and 
Savvis ITM would be in big trouble if CNAME chains weren't allowed.

$ dig

; <<>> DiG 9.3.4 <<>>
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5269
;; flags: qr rd ra; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 0

;      IN A

;; ANSWER SECTION: 2566  IN CNAME  52 IN CNAME   52 IN CNAME    3790  IN CNAME  1189 IN  CNAME  8  IN A  8  IN A  8  IN A  8  IN A  8  IN A  8  IN A  8  IN A  8  IN A

Barry Margolin, barmar at
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

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