[SOLVED] Re: bind listening on UDP port 53 using 2 fd

Matus UHLAR - fantomas uhlar at fantomas.sk
Mon Jan 25 13:33:16 UTC 2021

On 25.01.21 14:05, Bernardo wrote:
>Yes. This causes serious problems.
>The problem is that these perfectly valid configuration lines in
>/etc/named.conf file (provided that is the IPv4 address of
>your DNS server, it doesn't matter if it is a primary or secondary) will
>cause you a lot of trouble.
>query-source address;
>notify-source port 53;
>transfer-source port 53;
>These configuration lines will cause you problems as described in my post (
>BIND ignores "packets received correctly" ) from January 2020.
>It seems that this is a know issue since BIND 9.16.1 version: UDP network
>ports used for listening can no longer simultaneously be used for sending

which means, that the "port 53" is what causes problems and the rest can
stay there.

If you only have interace address "" (except loopback, if
course), or if that is the primary address of your interface, those
defitions are useless, otherwise you should keep them there.

>El lun, 25 ene 2021 a las 11:13, Matus UHLAR - fantomas (<uhlar at fantomas.sk>)
>> On 23.01.21 12:44, Bernardo wrote:
>> >Finally I've found the solution.
>> >The problem seems to be caused by a known issue since BIND version 9.16.1
>> >
>> >Commenting out these lines in /etc/named.conf solves the issue:
>> >
>> >query-source address;
>> >notify-source port 53;
>> >transfer-source port 53;
>> this should not cause a problem and may cause troubles when
>> is not the primary address.
>> the "port 53" is usually useless (unless you have stateless firewall) and
>> may be what caused your problem.

Matus UHLAR - fantomas, uhlar at fantomas.sk ; http://www.fantomas.sk/
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