Many A-records

Barry Margolin barmar at alum.mit.edu
Thu Apr 8 19:21:47 UTC 2004


In article <c540ko$25n7$1 at sf1.isc.org>,
 Jonathan de Boyne Pollard <J.deBoynePollard at Tesco.NET> wrote:

> JL> Every time you create a CNAME where you could have used an A
> JL> record you create a situation where every resolver looking 
> JL> for your service must do two lookups instead of one.  
> 
> BM> Unless the server is authoritative for both the CNAME record 
> BM> and its target.  In that case the server will return both 
> BM> records, [...]
> 
> If the first client-side aliase leads out of the server's bailiwick, then 
> the resolving proxy DNS server _still_ needs to perform further lookups, 
> because the second alias in the chain will be discarded as poison.

Yes.  That's not what I was talking about -- I specifically said "if the 
server is authoritative for both the CNAME record and its target."  This 
isn't an uncommon configuration, e.g. for things like:

@   IN A 1.2.3.4
www IN CNAME @

so that the web site can be referred to as either <domain> or 
www.<domain>.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***


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