Root hints

[Evan Hunt]

On Tue, Oct 06, 2015 at 05:42:52PM +0000, Jack Tavares wrote:
> Since the H root server IP address will be changing I have a question:
> http://h.root-servers.org/renumber.html
> 
> how does bind get the root servers these days?
> I think the code includes a set.

There's a copy of the hints built in to named (it's in lib/dns/rootns.c).
We update it periodically (most recently to add an AAAA for D root a few
years ago), and will do so again when the H address changes.  IIRC that
change is planned for the end of this year, so the change will be included
in BIND 9.9.9, 9.10.4, and 9.11.0.

> Is there a provision to query a known address to get an update?

When named starts up, if it's running as an iterative resolver (as opposed
to a forwarder), the first thing it does is send a "priming" query to the
hint servers looking for a new up-to-date NS RRset.

In servers that still have the old hints, H wouldn't respond to the
priming query, but all the other root servers would, and named
would learn the new address for H from one of them, so H will work
fine thereafter.

-- 
Evan Hunt -- each at isc.org
Internet Systems Consortium, Inc.