[dns-operations] difference between several NS with several glue

[Dave Warren]

On 2014-07-24 02:52, han feng wrote:
> For a zone(like  example.com) owner, what’s the difference between these following two configurations:
>
> example.com.	86400	NS 	a.example.net.
> example.com.	86400 	NS 	b.example.net.
> example.com. 	86400 	NS 	c.example.net.
>
> a.example.net. 3600 A  1.1.1.1
> b.example.net. 3600 A  2.2.2.2
> c.example.net. 3600 A  3.3.3.3
>
> and
>
> example.com.	86400	NS 	a.example.net.
>
> a.example.net. 3600 A  1.1.1.1
> a.example.net. 3600 A  2.2.2.2
> a.example.net. 3600 A  3.3.3.3
>
>
> Since all the name servers are in example.net zone, these two configure both specify three name servers
> for example.com zone and will be affected if example.net name server failed.  And the latter configuration 
> will generate smaller package. But the first configuration seems more common, so what’s the benefit?

>From what I understand, when 1.1.1.1 fails to respond, all of
a.example.net will be considered bad, so 2.2.2.2 and 3.3.3.3 won't be
queried at all, and a resolver will return a SERVFAIL.

So the above-described configuration gives you rudimentary load
balancing, but no redundancy. However, if a.example.net happens to be
reachable via multiple IP addresses (IPv4 and IPv6, for example), it
might make sense to use the same name.

-- 
Dave Warren
http://www.hireahit.com/
http://ca.linkedin.com/in/davejwarren