underscore in A or PTR records
marka at isc.org
Wed Feb 17 08:27:35 UTC 2021
The SRV and TXT records usage is depending on underscore not being part of a hostname.
The separator in hostname labels is dash. e.g. my-host.example.net
_ssh._tcp.example.net SRV can be safely deployed because there are no legal hostnames
starting with _ssh and _tcp.
Hostname (and mail domain) syntax is defined by RFC 952 as modified by RFC1123 (allows
labels to start with digits.
PTR records it depends on usage.
> On 17 Feb 2021, at 19:13, ONRUBIA AVILES Carlos (CCS/MST) <carlos.onrubia.aviles at proximus.com> wrote:
> Hello ,
> I face the following problem è bind do not accept an A record with underscore:
> Example: example_try A 184.108.40.206
> Same for a PTR:
> Example: 220.127.116.11 PTR example_try
> Is it absolutely forbidden to have in such cases an ‘_’?
> I know that it is possible for SRV or TXT records.
> Thanks in advance to clarify the situation and sorry if this question has already be asked.
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Mark Andrews, ISC
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PHONE: +61 2 9871 4742 INTERNET: marka at isc.org
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