According to RFC1034 and 2181, a PTR record using a CNAME is not permitted. I believe this to still be correct, postfix certainly doesn't work with a CNAME when it does a reverse lookup.
Any comments?
thanks. Per
On 2018-05-30 16:44, Per Jessen wrote:
According to RFC1034 and 2181, a PTR record using a CNAME is not permitted. I believe this to still be correct, postfix certainly doesn't work with a CNAME when it does a reverse lookup.
Postfix certainly does as:
$ dig +short 50.131.144.213.in-addr.arpa. ptr 50.63-28.131.144.213.in-addr.arpa. citadel.ch.unfix.org.
would otherwise not work.... and that trick of CNAME'ing in-addr.arpa space is used a lot by ISPs to delegate space (as per the above example where init7 forwards them to my nameservers).
There is also a nice RFC on that:
https://www.ietf.org/rfc/rfc2317.txt
Greets, Jeroen
Jeroen Massar wrote:
On 2018-05-30 16:44, Per Jessen wrote:
According to RFC1034 and 2181, a PTR record using a CNAME is not permitted. I believe this to still be correct, postfix certainly doesn't work with a CNAME when it does a reverse lookup.
Postfix certainly does as:
$ dig +short 50.131.144.213.in-addr.arpa. ptr 50.63-28.131.144.213.in-addr.arpa. citadel.ch.unfix.org.
would otherwise not work.... and that trick of CNAME'ing in-addr.arpa space is used a lot by ISPs to delegate space (as per the above example where init7 forwards them to my nameservers).
There is also a nice RFC on that: https://www.ietf.org/rfc/rfc2317.txt
Okay, thanks for clarifying that - I was wondering. I don't why my postfixes come up with host name 'unknown'.
On 2018-05-30 17:35, Per Jessen wrote:
Jeroen Massar wrote:
On 2018-05-30 16:44, Per Jessen wrote:
According to RFC1034 and 2181, a PTR record using a CNAME is not permitted. I believe this to still be correct, postfix certainly doesn't work with a CNAME when it does a reverse lookup.
Postfix certainly does as:
$ dig +short 50.131.144.213.in-addr.arpa. ptr 50.63-28.131.144.213.in-addr.arpa. citadel.ch.unfix.org.
would otherwise not work.... and that trick of CNAME'ing in-addr.arpa space is used a lot by ISPs to delegate space (as per the above example where init7 forwards them to my nameservers).
There is also a nice RFC on that: https://www.ietf.org/rfc/rfc2317.txt
Okay, thanks for clarifying that - I was wondering. I don't why my postfixes come up with host name 'unknown'.
Where does postfix say 'unknown'? In the prepended "Received: from ..." header? in logs?
Can be many reasons why it does not trust the originally provided data, especially as HELO/EHLO can be spoofed. Also depends on the resolver etc etc, many factors ;)
Greets, Jeroen
Am 30.05.2018 um 17:35 schrieb Per Jessen:
Okay, thanks for clarifying that - I was wondering. I don't why my postfixes come up with host name 'unknown'.
afaik postfix logs "unknown" as well if it is not a FcrRDNS means the hostname retrieved from a PTR query should forward resolve again to the ip address.
Cheers
tobi
Tobi wrote:
Am 30.05.2018 um 17:35 schrieb Per Jessen:
Okay, thanks for clarifying that - I was wondering. I don't why my postfixes come up with host name 'unknown'.
afaik postfix logs "unknown" as well if it is not a FcrRDNS means the hostname retrieved from a PTR query should forward resolve again to the ip address.
Yes, that is correct. Provided postfix works with a PTR with a CNAME, that bit is okay.
Per,
I just want to throw in the following:
In case you want to subdelegate a part of a PTR zone, this seems to be the recommended way to do it:
https://simpledns.com/kb/77/how-to-sub-delegate-a-reverse-zone
jeroen, any comment on this?
cheers
Ralph ----- Am 30. Mai 2018 um 16:44 schrieb Per Jessen per.jessen@enidan.ch:
According to RFC1034 and 2181, a PTR record using a CNAME is not permitted. I believe this to still be correct, postfix certainly doesn't work with a CNAME when it does a reverse lookup.
Any comments?
thanks. Per
-- Per Jessen, Zürich (28.6°C) http://www.dns24.ch/ - free dynamic DNS, made in Switzerland.
swinog mailing list swinog@lists.swinog.ch http://lists.swinog.ch/cgi-bin/mailman/listinfo/swinog
On 2018-05-31 17:55, Ralph Krämer wrote:
Per,
I just want to throw in the following:
In case you want to subdelegate a part of a PTR zone, this seems to be the recommended way to do it:
https://simpledns.com/kb/77/how-to-sub-delegate-a-reverse-zone
jeroen, any comment on this?
As per previous reply on this thread, the IETF way to do it is detailed in: https://www.ietf.org/rfc/rfc2317.txt
Anything that needs clarification there?
Greets, Jeroen
-
Jeroen Massar -
Per Jessen -
Ralph Krämer -
Tobi