[Pdns-users] Question about Multiple CNAMES

Clint Martin clintm at laplink.com
Fri Oct 8 19:31:03 UTC 2004


I have PDNS 9.16 with the gmysql backend configured to serve several
domains.  I am very impressed with PDNS btw.. 

One of the requirements for some of the services we have is the ability
to point one DNS name at multiple machines.

relay.dev.domain.net		CNAME	relay00.dev.domain.net
relay.dev.domain.net		CNAME	relay01.dev.domain.net

relay00.dev.domain.net	A
relay01.dev.domain.net	A

Nothing too complex.

Querying for relay.dev.domain.net works quite well. It returns both
CNAME records.  However only the last A record is returned not both...

# dig relay.dev.domain.net

; <<>> DiG 8.3 <<>> relay.dev.domain.net
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44206
;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
;;      relay.dev.domain.net, type = A, class = IN

Relay.dev.domain.net.  30S IN CNAME  relay00.dev.domain.net.
test.dev.domain.net.  30S IN CNAME  relay01.dev.domain.net.
relay01.dev.domain.net.  5M IN A

;; Total query time: 2 msec
;; FROM: vivien.camelot.intl to SERVER:
;; WHEN: Fri Oct  8 12:17:44 2004
;; MSG SIZE  sent: 42  rcvd: 102

Is this behavior by design?  I would think that if it bothered to return
any of the A records, it should return them both..   
I'm not real well versed in the relevant RFC's so I don't know if this
is right or not..   

I'm concerned that because it is only returning one of the A records,
that most resolvers won't bother to resolve the other CNAME,
And consequently, will never try to use the other machine.  Am I worried
about nothing?

Clint Martin
Network Administrator
LapLink Software Inc.
PGP Fingerprint: 0B38 734C CB87 B51D 287F 9EC3 B97E 5E38 7A30 ED4B 
Public key available upon request

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