The Department of Work and Pensions, UK has an entire /8 nanog at nanog.org

Thu Sep 20 02:09:20 UTC 2012

On Wed, Sep 19, 2012 at 06:46:54PM -0700, Jo Rhett wrote:
> 
> For these networks to have gateways which connect to the outside, you
> have to have an understanding of which IP networks are inside, and
> which IP networks are outside. Your proxy client then forwards
> connections to "outside" networks to the gateway. You can't use the
> same networks inside and outside of the gateway. It doesn't work. The
> gateway and the proxy clients need to know which way to route those
> packets.

It works fine if the gateway has multiple routing tables (VRF or
equivalent) and application software that is multiple-routing-table
aware.

Not disagreeing at all with the point many are making that "not on the
Internet" doesn't mean "not in use".  Many people for good reason
decide to use globally unique space on networks that are not connected
to the Internet.  But the idea that you *can't* tie two networks
togethor with an application gateway unless the address space is unique
is an overstatement.  It's just harder.

     -- Brett