Private use of non-RFC1918 IP space

Patrick W. Gilmore patrick at
Mon Feb 2 15:59:13 UTC 2009

On Feb 2, 2009, at 10:57 AM, Jeffrey Ollie wrote:
> On Mon, Feb 2, 2009 at 9:48 AM, Trey Darley <trey at>  
> 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 recommend against it, because even though the network is not
> connected to the Internet now you never know what the future holds.
> Even if it's never connected there are always things that seem to pop
> up and cause problems.
> Also, if you're address allocation policy has been so badly managed
> that you've run out of space in adding more IPs to the pool
> isn't going to help for very long.

It will if you manage it better.

Fortunately, there's a /12 and a /24 still left.  A /12 is more space  
than 99.99% of the networks on the Internet need, so why wouldn't that  
suffice instead of using "real" space.


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