Many A-records

[John S. Giltner, Jr.]

Jonathan de Boyne Pollard wrote:
> JSGJ> If you run and manage the DNS servers and zones, then using
> JSGJ> CNAME's instead of A records is fine.  But in the end you 
> JSGJ> still have multiple records pointing to a single address.  
> JSGJ> Using CNAME's can make life easier, as if you change a hosts 
> JSGJ> IP address, you update one record and you are done.  If you 
> JSGJ> move a virtual web site to another host, you just change the
> JSGJ> CNAME.
> 
> It's not "CNAME" resource records that make life easier in such situations. 
> It is _aliases_.  But there are more than one type of aliases.  "CNAME"
> resource records are merely _client-side_ aliases.  But there are also several
> kinds of _server-side_ aliases.
> 
> ISC's BIND supports only two sorts of server-side aliases, wildcards and
> "whole 'zone'" server-side aliases.  With the latter form of server-side
> aliases, for example, one _still_ "updates one record" and "is done". 
> Consider the case where one has multiple zones ("example.net.",
> "example.org.", and "example.com.") all backed by the same "zone" file:
> 
> 	@   IN SOA  [...]
> 	@   IN NS   [...]
> 	@   IN MX   [...]
> 	www IN A    10.17.34.59
> 
> Changing that one "www" line in that one file would change the name->address
> mappings for "www.example.org.", "www.example.net.", and "www.example.com." in
> one fell swoop.
> 
> For aliasing, "CNAME" resource records are not the sole answer, and are often
> not even a good answer.  
> 
> And it is the _server-side_ aliasing features of a content DNS server
> softwares that are the better measure of how easy life can be made in such
> situations.
> 

I have a basic understanding of DNS, not really in-depth.  My idea of the:

	CUST CNAME --> YOUR CNAME --> A record --> IP address

was a attempt to reslove my understanding fih's issue.  Where "YOUR 
CNAME" was a CNAME in a zone that fih owns and manages  Which was 
basically, he does not want to have to tell his customers to update 
their DNS entries for host names that point to servers he runs.

I am not sure if I really understand where he is coming from.  Some of 
his ideas do seem to be based on how things worked years ago, but not today.