0-TTL when querying "invalid" soa

[Tom]

Perfect.., many thanks for your hints.

Tom


On 29.01.19 16:33, Tony Finch wrote:
> Tom <tomtux007 at gmail.com> wrote:
>>
>> We're running BIND-9.12.3-P1 on our authoritative servers and we have the same
>> behavior with 0-ttl with a invalid soa-query. Is this bind-specific? Why does
>> an invalid soa-record responds with 0-ttl in the authority-section?
> 
> Funnily enough, this little obscurity came up elsewhere just last week.
> 
> I had the same question back in 2012:
> 
> https://lists.isc.org/pipermail/bind-users/2012-June/087843.html
> 
> https://tools.ietf.org/html/draft-andrews-dnsext-soa-discovery
> 
> The latter link explains the reason for this odd behaviour.
> 
> [ Last week we also discussed an odd bit of text in RFC 1035: "For
> example, SOA records are always distributed with a zero TTL to
> prohibit caching." But RFC 2181 said you must no longer do that. ]
> 
> https://twitter.com/fanf/status/1087708537600569344
> 
> Tony.
>