curious CNAME answer?

Mark Andrews marka at isc.org
Thu Feb 4 22:06:49 UTC 2010


In message <BLU149-W18AEC33C220B5F6D2440E585550 at phx.gbl>, MontyRee writes:
> Hello, all.
>  
> I have some curious question.
> below is a part of zone file at master dns(example.com).
>  
>  
> www                       IN      CNAME   www.down
> down                      IN       NS     ns3.example.com.
>  
> wehn I dig query like below at server,
>  
>  
> $ dig @dns.example.com www.example.com 
>  
>  
> the result is different..
>  
> if query from slave dns server,
>  
> 192.168.2.1.domain> xx.xx.xx.xx.30869:  45064* 2/2/2 CNAME[|domain]
>  
> and the answer is 
> www.example.com.   3600    IN      CNAME   www.down.example.com.
> www.down.example.com. 27   IN      A        10.10.1.3

You offer recursion to xx.xx.xx.xx and dig set recursion desired by
default so the CNAME is followed.

> if query from any other server, 
>  
> 192.168.2.1.domain> xx.xx.xx.xx.47127:  58823*- 1/2/2 CNAME[|domain]
>  
> and the answer is 
> www.example.com.   3600    IN      CNAME   www.down.example.com.

You don't offer recursion to this client so named returns a CNAME
and a referral to the child servers.

> my question is,
> Why the result is different by client?
> why first case answers A record also but the second case is cname only?
>  
>  
> Thanks in advance. 		 	   		  
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org



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