[Pdns-users] Creating a www CNAME in powerDNS Admin (mysql backend) automatically pointing to @

[Brian Candler]

On 23/01/2023 12:10, Andrea Biancalani wrote:
>
> my default template for new hosting is similar to this
>
>> @ SOA ...
>> @ NS ...
>> @ MX ...
>> @ A 192.0.2.1
>> @ AAAA 2001:db8::1
>> www A 192.0.2.1
>> www AAAA 2001:db8::1
>
> but if I try to use this template
>
>> @ SOA ...
>> @ NS ...
>> @ MX ...
>> @ ALIAS www. /*(added final dot)*/
>> www A 192.0.2.1
>> www AAAA 2001:db8::1
>
> I can resolve the www.foo.bar record, but when trying to resolve 
> foo.bar I get a "Server failed" answer ( dns-server is not able to 
> find foo.bar)

That is as expected. If you add the final dot to www, then you are 
forcing it to resolve the top-level name, literally just "www" (not 
"www.foo.bar"), which of course does not exist.

If this were a BIND zonefile, then "www" without the dot would have the 
current domain appended implicitly.  I haven't tried this with PDNS.

Also, alias records only work if you've configured pdns-auth with a 
resolver to be able to look them up.


>
> Trying to use a template like this instead, gave as result a "RRset 
> foo.bar. IN CNAME: Conflicts with pre-existing RRset"
>
>> @ SOA ...
>> @ NS ...
>> @ MX ...
>> @ CNAME www. /*(added final dot)*/
>> www A 192.0.2.1
>> www AAAA 2001:db8::1
>
That is forbidden by the RFCs. A CNAME cannot exist at the same position 
in the DNS tree as any other records: in your case above, you have SOA, 
NS and MX records with the same label, which conflict with it.


> that doesn't happens if I use the zone record as target of the CNAME
>
>> @ SOA ...
>> @ NS ...
>> @ MX ...
>> @ CNAME foo.bar. /*(added final dot)*/
>> www A 192.0.2.1
>> www AAAA 2001:db8::1

That should give the same error - it doesn't make any difference what 
the target of the CNAME is - except if the domain in question is 
foo.bar, then you have a CNAME from foo.bar pointing to foo.bar, which 
is meaningless anyway. It may have been silently discarded.
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