Using multiple DNS servers options - implementation note missing

[OndrejPacay]

File: engine/userguide/networking/default_network/configure-dns.md

Hi I have found (the hard way), that when you specify multiple --dns options on the command line (or in daemon.json) then name resolution works by default this way:

• fire DNS request to all nameservers provided
• use the first response ... even if it responds by not found ... in other words, there is no fixed 'hierarchy' when using those nameservers and the result can be random for hosts that are not resolved by all nameservers listed.

This behaviour is probably sometimes beneficial, but should be better documented since:

• does not work the same as in linux/unix ... there the other nameservers are queried only if the 1st is unreachable
• creates intermittent problems when combining an intranet-only nameserver with a public one. For example when resolving an intranet hostname in such setup it can happen that 8.8.8.8 responds first that the hostname is not found and the resolution fails. ....in contrast it will resolve ok, when the intranet nameserver responds first.

Regards, Ondrej

[nigelpoulton]

Wondering if this should be filed as a potential bug against Engine @thaJeztah ??

I'd at least want someone to confirm this is intended behavior before documenting it.

[docker-robott]

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[docker-robott]

There hasn't been any activity on this issue for a long time.
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[docker-robott]

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