Secondary DNS Servers

Kevin Darcy kcd at
Wed Jan 15 17:50:20 UTC 2003

lumux wrote:

>Hi All,
>Could anyone please answer the following for me:
>If a DNS server requests the record for a domain, but the primary server is
>unavailable and the record is retrieved from the secondary DNS server, how
>log will the DNS server continue using secondary server over the primary?
I'm not sure exactly how you're using the term "primary" and 
"secondary". Order is not significant amongst the nameservers in an NS 
RRset, but most nameserver implementations will prefer *faster* NS'es 
over slower ones. So if one of the NS'es, which is normally faster, goes 
unavailable, then the time it takes for it to be preferred again after 
being restored depends on how *much* faster it is and how often it 
happens to be queried from any other given nameserver -- they all have 
to "re-learn" about the response speed of the restored nameserver.

                                                - Kevin

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