Private use of non-RFC1918 IP space

Justin M. Streiner streiner at
Mon Feb 2 16:04:57 UTC 2009

On Mon, 2 Feb 2009, Trey Darley wrote:

> Some colleagues and I are running into a bit of a problem. We've been
> using RFC 1918 Class A space but due to the way subnets have been
> allocated we are pondering the use of public IP space. As the network in
> question is strictly closed I don't anticipate any problems with this as
> the addresses would be unambiguous within our environment. I'm curious if
> anyone else is doing this.
> I'd be very interested in corresponding off-list with anyone who's in a
> similar position.

Technically, yes you can use non-RFC1918 space in this way, but is 
definitely not a good idea.  The needs of the people using the network 
could change at some point in the future, where some degree of Internet 
connectivity is needed, at which point your support headaches would 
multiply if you used non-1918 space in this manner.

Is there a reason that other 1918 address ranges (172.16/12, 192.168/16)
could not be used?


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