Zone Forwarding and Avertised NS

Kevin Darcy kcd at
Fri Oct 20 01:04:50 UTC 2006

April wrote:
> If the forwarder is not included as the avertised NS, will the next
> time the forwarding server goes to the avertised NS, instead of the
> specified forwarder?  
No, it won't start going to the published NS'es just because it saw them 
on a previous query, *however*, if you have a forwarding mode of 
"forward first" specified (or no forwarding mode at all, since, 
surprisingly, "forward first" is the default mode), then your resolver 
*may* fall back to iterative resolution if the forwarders become 
unavailable, and if the NS records for the zone still happen to be in 
the cache, it'll use them. So, indirectly and under certain 
circumstances, it is possible that those NS records may cause some of 
your queries to be sent to the nameservers listed therein.
> If so, any way to force it goes to the specified
> forwarder only?
A forwarding mode of "forward only" is sufficient to prevent your 
resolver from ever using NS records to determine what nameservers to 
query for a given zone (unless of course forwarding is overridden 
somehow at that point in the hierarchy or higher). "forward only" is the 
mode one should always use when using forwarding to deal with a 
connectivity issue/challenge (e.g. being firewalled off from direct 
Internet querying). "Forward first", on the other hand, is strictly of 
use in optimizing query performance/latency for machines that already 
have the requisite connectivity to resolve anything they want _without_ 
using forwarding.

                        - Kevin

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