about the wild record

[Warren Kumari]

On Oct 15, 2012, at 3:45 AM, pangj <pangj at riseup.net> wrote:

> 于 2012-10-15 15:38, Cathy Almond 写道:
>> On 15/10/12 05:23, pangj wrote:
>>> Hello,
>>> 
>>> I have setup a wild record for cloudns.tk, the record:
>>> 
>>> *.cloudns.tk.  300     IN      A       209.141.54.207
>>> 
>>> And I added another A record as this:
>>> 
>>> s1.test.cloudns.tk.     300     IN      A       8.8.8.8
>>> 
>>> After adding this record, the record of test.cloudns.tk gets lost, it
>>> does't match the wild record anymore.
>>> 
>>> "dig test.cloudns.tk" gets nothing.
>>> 
>>> Can you help explain it? thanks in advance.
>> 
>> It's subtle.
>> 
>> Wildcards match where there are no labels already.
>> 
>> By adding record s1.test.cloudns.tk, you're implicitly creating domain
>> test.cloudns.tk.  It's empty, but it exists.
>> 
> 
> But I didn't define a zone "test.cloudns.tk" (neither NS nor soa defined for it), why this domain exists?

You created s1.test.cloudns.tk -- when you did this, you "automatically"  created test.cloudns.tk (if you had created a.b.c.d.e.cloudns.tk you would also have created e.cloudns.tk, d.e.couldns.tk, c.d.e.cloudns.tk, b.c.d.e.cloudns.tk).

The DNS is basically a tree structure -- in order to have a leaf s1.test.cloudns.tk, there needs to be a "branch" (test.cloudns.tk) for it to hang on. By adding the s1.test.cloudns.tk leaf you also make the branch exist.

There *is* in fact an SOA for test.cloud.tk: 
dig SOA +nocomment +nostats test.cloudns.tk

; <<>> DiG 9.9.2 <<>> SOA +nocomment +nostats test.cloudns.tk
;; global options: +cmd
;test.cloudns.tk.		IN	SOA
cloudns.tk.		226	IN	SOA	ns0.cloudwebdns.com. support.cloudwebdns.com. 1048 7200 1800 604800 300

It is the SOA for clouds.tk. 

W

> 
> Thanks Cathy.
> 
> _______________________________________________
> Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list
> 
> bind-users mailing list
> bind-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/bind-users

--
The duke had a mind that ticked like a clock and, like a clock, it regularly went cuckoo.

    -- (Terry Pratchett, Wyrd Sisters)