[Pdns-users] powerdns answers different on duplicate mx records

Martin Kuchar lists at nss.wproduction.cz
Wed May 26 11:05:02 UTC 2004


I thing, (but not sure) that duplicate records are not allowed in dns
response. The difference can be in case that response is parsed from
beginnig in one case and from the end in another case. In both cases only
first (or only last) from duplicated records is shown.

Martin Kuchar

> -----Original Message-----
> From: pdns-users-bounces at mailman.powerdns.com 
> [mailto:pdns-users-bounces at mailman.powerdns.com] On Behalf Of 
> Simon Ostengaard
> Sent: Wednesday, May 26, 2004 11:44 AM
> To: 'pdns-users at mailman.powerdns.com'
> Subject: [Pdns-users] powerdns answers different on duplicate 
> mx records
> 
> I have a zone hosted on a powerdns server with mysql backend 
> with two mx
> records pointing to the same server. i.e.
> 
> mysql> select * from records where name = 'example.com' and 
> type = 'mx'\G
> 
> *************************** 1. row ***************************
>          id: 221832
>   domain_id: 34786
>        name: example.com
>     content: mail1.example.com
>         ttl: 60
>        prio: 50
>        type: MX
> create_date: 20040526075242
> change_date: 1085557962
>      hidden: 0
>    readonly: 0
> *************************** 2. row ***************************
>          id: 222723
>   domain_id: 34786
>        name: example.com
>     content: mail2.example.com
>         ttl: 60
>        prio: 75
>        type: MX
> create_date: 20040526081803
> change_date: 1085559483
>      hidden: 0
>    readonly: 0
> *************************** 3. row ***************************
>          id: 222722
>   domain_id: 34786
>        name: example.com
>     content: mx1.example.com
>         ttl: 60
>        prio: 25
>        type: MX
> create_date: 20040526081729
> change_date: 1085559449
>      hidden: 0
>    readonly: 0
> *************************** 4. row ***************************
>          id: 165835
>   domain_id: 34786
>        name: example.com
>     content: mail1.example.com
>         ttl: 60
>        prio: 50
>        type: MX
> create_date: 20031021093913
> change_date: 1066729153
>      hidden: 0
>    readonly: 0
> *************************** 5. row ***************************
>          id: 165836
>   domain_id: 34786
>        name: example.com
>     content: mail2.example.com
>         ttl: 60
>        prio: 20
>        type: MX
> create_date: 20031117113922
> change_date: 1069069162
>      hidden: 0
>    readonly: 0
> 5 rows in set (0.00 sec)
> 
> A quit odd setup, but still valid though.
> 
> When I do an mx look up on the server I get the two records 
> with the lowest
> id:
> 
> user at foobar:~$ dig @ns1.example.com example.com mx
> 
> ; <<>> DiG 9.2.1 <<>> @ns1.example.com example.com mx
> ;; global options:  printcmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9232
> ;; flags: qr aa rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0
> 
> ;; QUESTION SECTION:
> ;example.com.                   IN      MX
> 
> ;; ANSWER SECTION:
> example.com.            60      IN      MX      50 mail1.example.com.
> example.com.            60      IN      MX      20 mail2.example.com.
> example.com.            60      IN      MX      25 mx1.example.com.
> 
> ;; Query time: 6 msec
> ;; SERVER: 80.80.19.154#53(ns1.example.com)
> ;; WHEN: Wed May 26 09:33:35 2004
> ;; MSG SIZE  rcvd: 108
> 
> But when I do an axfr look up I get the two records with the 
> highest id:
> 
> user at foobar:~$ dig @ns1.example.com example.com axfr
> 
> ; <<>> DiG 9.2.1 <<>> @ns1.example.com example.com axfr
> ;; global options:  printcmd
> example.com.            40001   IN      SOA     ns1.example.com.
> user.example.com 1085559483 10800 3600 604800 40001
> example.com.            86400   IN      NS      ns2.example.com.
> example.com.            86400   IN      NS      ns1.example.com.
> www.example.com.        60      IN      A       <an ip address>
> example.com.            60      IN      MX      50 mail1.example.com.
> example.com.            60      IN      MX      75 mail2.example.com.
> example.com.            60      IN      MX      25 mx1.example.com.
> example.com.            40001   IN      SOA     ns1.example.com.
> user.example.com. 1085559483 10800 3600 604800 40001
> ;; Query time: 9 msec
> ;; SERVER: 80.80.19.154#53(ns1.example.com)
> ;; WHEN: Wed May 26 09:34:21 2004
> ;; XFR size: 9 records
> 
> Can anybody explain this behaviour?
> 
> Best regards,
> 
> Simon Ƙstengaard
> Systems Administrator
> 
>  
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