about the wild record
Warren Kumari
warren at kumari.net
Mon Oct 15 12:30:41 UTC 2012
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.
>
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