[nsd-users] What is the selection order of forward-first NSs? sequential? random? IPv6 before/after IPv4?

PGNet Dev pgnet.dev at gmail.com
Thu Jun 10 12:00:00 UTC 2021

On 6/9/21 10:50 AM, George Thessalonikefs via nsd-users wrote:
> I think you posted on the wrong mailing list :)

oops! yep.

> I'll reply here and include unbound-users also.
> If you want to reply further please drop nsd-users and let us continue the 
> discussion only on the unbound-users mailing list as to not generate noise here.


> On 07/06/2021 21:31, PGNet Dev via nsd-users wrote:
>> On my server, I config
>> what's the order policy for those forward-addr's?
>> Is the forward-addr used randomly, or sequentially, selected from that list?
> Randomly between the fastest servers (in the <400ms band). Unbound will keep 
> probing the other servers to keep updated metrics for them in case they become 
> fast enough (<400ms). You can read more about it at 
> https://www.nlnetlabs.nl/documentation/unbound/info-timeout/.
>> Is there any unbound preference for IPv4 vs IPv6 forward-addrs?
> There are the 'prefer-ip4:' and 'prefer-ip6:' options if you want to do that.

in the case of

     do-ip4: yes
     do-ip6: yes
     prefer-ip4: no
     prefer-ip6: yes

iiuc, then, it's strictly a preference, and _will_ fallback to the ip4 if ip6 
'pref' fails ?

Reading for 'prefer-ip4',

" Useful if the IPv6 netblock the server has, the entire /64 of that is not 
owned by one operator  and  the reputation of the netblock /64 is an issue, 
using IPv4 then uses the IPv4 filters that the upstream servers have."

tbh I've no sense for the magnitude of that issue.

I'd guess it's a non-zero-sized problem.  But generally _worth_ setting a 

Are the settings' defaults (prefer-ipX = no) chosen as typically *recommended* 
-- vs simplest config -- values?

>> Does the preference respect /etc/gai.conf?
> No.

thx o/

More information about the Unbound-users mailing list