Private use of non-RFC1918 IP space

Skeeve Stevens skeeve at
Wed Feb 4 00:57:36 UTC 2009


Following myself up, and referencing a link someone else gave me in regards
to IPv6

Has the entry:

Private use of other reserved addresses

Several other address ranges, in addition to the official private ranges,
are reserved for other or future uses, including and[1].
In recent years, large companies have begun to use this address space
internally. Though discouraged, it appears to have become an accepted
practice among larger companies to use these reserved address spaces when
connecting two private networks, to eliminate the chance of address
conflicts when using standards-based private ranges.


Now I'm not using this as justification.... just interesting to see people
have put it up there, and comment that a lot of large companies are using
1/8 and 2/8 for private networking.


-----Original Message-----
From: Skeeve Stevens [mailto:skeeve at] 
Sent: Wednesday, 4 February 2009 9:48 AM
To: 'David Conrad'; 'Bruce Grobler'
Cc: 'NANOG list'
Subject: RE: Private use of non-RFC1918 IP space

OK, I will make an (what looks to this list) embarrassing admission.

We use for our internal ranges, but this is on a small scale.

We do it because of the kind of business we do... we manage many other much
larger networks which already use every possible overlapping RFC1918 network
you can imagine... we have half a dozen networks using 192.168.0, and even
more using many varied masks in the  We already have issues with
the overlapping networks as is, without making it worse for us by using on
of them.

I chose to go the path because:

- It wont conflict with my customers and us doing our business
- As long as it is not APNIC who gets it, the chances of it conflicting will
be extremely minimal (rolls dice)
- We don't design customer networks with non-RFC1918 ranges unless there is
some extreme reason
- Yes it is potentially allocate-able in the future, but if it happens I
will deal with it then - just renumber or see the next point
- We will be fully IPv6 within 6-9 months with a separate VLAN which will
support legacy equipment with NAT-PT... this will still be an issue
interconnecting to customer networks, but we will think of something.


-----Original Message-----
From: David Conrad [mailto:drc at] 
Sent: Tuesday, 3 February 2009 6:48 AM
To: Bruce Grobler
Cc: NANOG list
Subject: Re: Private use of non-RFC1918 IP space

On Feb 2, 2009, at 8:10 AM, Bruce Grobler wrote:
> Most ISP's, if not all, null route therefore you shouldn't
> encounter any problems using it in a private network.

Is this true?

This will cause endless entertainment when IANA allocates  
sometime within the next two or three years...


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