Re: What is the difference between "No address associated with name" and "Unknown host"
- From: Nagy László Zsolt <nagylzs@xxxxxxxxxxx>
- Date: Mon, 04 Dec 2006 21:11:37 +0100
a@xxxxxxxx wrote:
What is the difference between "No address associated with name" and "Unknown host":If the host is unknown, then it means that the primary domain name server is not registered for the given domain. Because the domain name server cannot be found, it is not possible to tell the IP address of the given hostname.
$ ping accounts.eirtrade.ie
ping: cannot resolve accounts.eirtrade.ie: No address associated with name
and
$ ping accounts.eirtrade.i
ping: cannot resolve accounts.eirtrade.i: Unknown host
You get the second message when there is a primary domain name server for the given domain, but it does not return any IP address for your (named) address. It means that there is no A record for the given hostname.
For me, I get these results:
#ping acconts.eirtrade.ie
ping: cannot resolve acconts.eirtrade.ie: Unknown host
#ping eirtrade.ie
ping: cannot resolve eirtrade.ie: No address associated with name
If you have the "dig" command available on your machine, you can read its documentation, and play with it. It will make things clear. Look below: in the first case, there is no A record, but there is a SOA record. However, the hostname of the SOA is different from the queried hostname. In the second case, there is no A record, there is a SOA and the hostname of the SOA and the queried hostname are the same. So in the first case, we cannot know if the host is registered at all. In the second case, the hostname is registered for sure, but it has no A record. (However, subdomains like www.eirtrade.ie can have A records...)
#dig accounts.eirtrade.ie
; <<>> DiG 9.3.2 <<>> accounts.eirtrade.ie
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50610
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;accounts.eirtrade.ie. IN A
;; AUTHORITY SECTION:
eirtrade.ie. 10515 IN SOA auth01.ns.eircom.net. hostmaster.eircom.net. 2001031301 28800 7200 604800 86400
;; Query time: 1 msec
;; SERVER: 195.228.240.249#53(195.228.240.249)
;; WHEN: Mon Dec 4 15:02:25 2006
;; MSG SIZE rcvd: 105
#dig eirtrade.ie
; <<>> DiG 9.3.2 <<>> eirtrade.ie
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 932
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; QUESTION SECTION:
;eirtrade.ie. IN A
;; AUTHORITY SECTION:
eirtrade.ie. 10800 IN SOA auth01.ns.eircom.net. hostmaster.eircom.net. 2001031301 28800 7200 604800 86400
;; Query time: 37 msec
;; SERVER: 195.228.240.249#53(195.228.240.249)
;; WHEN: Mon Dec 4 15:03:17 2006
;; MSG SIZE rcvd: 96
Best,
Laszlo
p.s.: I think I'm right, but please do not trust me blindly. :-)
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