Blackhole DNS

Mark_Andrews at Mark_Andrews at
Fri Feb 22 00:52:53 UTC 2002

> On Thu, Feb 21, 2002 at 09:59:49PM +0000, Martin Stewart wrote:
> > When a server is being accessed by clients with private addresses 
> > (RFC1918) is it best practice to make the server's caching DNS server 
> > authoritative for
> This shouldn't be an issue. If a server is reachable by clients with
> RFC1918 IPs, then the local nameservers should already be able to
> resolve those IPs. This is simply proper administration.
> Backbone routers should/would/will not route RFC1918 IPs so if you don't
> have any local IPs like that, a server should never see them, and not
> need to resolve them.
> > I've recently seen a problem which I claimed might have been caused by an 
> > outage (or us not being able to reach) the blackhole servers at blackhole-
> > and I was wondering how other people solved that issue.
> See above, it shouldn't be a problem. If it is, set a local nameserver
> as authoritative for those IP ranges/zones and make any caches forward
> requests for those zone/ranges to your authoritative nameservers.
> -- 
> Nate Campi     Job: hostmaster at and root at
> "Confucius say: He who play in root, eventually kill tree." 
	You have missed the whole point of the question.  It is
	irrelvent whether packet with RFC 1918 addresses are forwarded
	through the Internet or not.

	The "caching" server here is likely to have both a RFC 1918
	address and a non RFC 1918.  It will be getting queries for
	the relevant parts of that correspond to the
	RFC 1918 address being used.  These queries should be
	answered by this server (or another internal server) and NOT
	looked up on the Internet.

	This is the same way as (
	should be on every caching server.  It is address space private
	to the host.  Queries for should be answered

	For IPv6 the following should all be local along with the
	versions. (link local) (site local)

Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at

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