root hints operation

[/dev/rob0]

On Mon, Nov 16, 2015 at 06:37:36PM -0700, Grant Taylor wrote:
> In light of the upcoming H-root server changing addresses I wanted 
> to confirm how BIND uses root hints.
> 
> It's my understanding that BIND has a compiled in version of the 
> root hints -and- a root hints file that can easily be updated.

You either specify a hints file to use, or use the compiled-in root 
hints.

> This information is used to prime named as it starts up in such as 
> it takes an IP for one of the root servers and attempts a to query 
> to update the root hint server name to IP mappings.  I believe that 
> named will cycle through all of the IPs in the root hints file 
> until it finds a server that it can query and update all of the 
> root server names / IPs in memory.  From and then continues running 
> with that updated information.
> 
> As such, I think BIND will continue operating with little, if any, 
> ill effect if people don't update their root hints file 
> immediately. (Though ideally people should update.)

Since the beginning of DNS, there has not been enough change to root 
hints so as to cause operational problems.

> Will someone take a moment and confirm, or correct, my 
> understanding of how root hints work in BIND?

I think this should answer your questions:

https://www.isc.org/blogs/h-root-will-change-its-addresses-on-1-december-2015-what-does-this-mean-for-you/
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