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<div class="moz-cite-prefix">On 12/13/2013 09:55 PM, Edward Holcroft
wrote:<br>
</div>
<blockquote
cite="mid:CAN8XfE9gUUZ6jF296x=UPQ7OqK8BAK_p25BsxybcCyug9u=fkw@mail.gmail.com"
type="cite">
<div><font face="arial, sans-serif">Came across this from which
glean that <a moz-do-not-send="true" href="http://5.0.0.0/8"
target="_blank">5.0.0.0/8</a> was not always publicly
allocated:</font></div>
<div><font face="arial, sans-serif"><br>
</font></div>
<div><font face="arial, sans-serif"><a moz-do-not-send="true"
href="http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_10-3/103_awkward.html"
target="_blank">http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_10-3/103_awkward.html</a></font><br>
</div>
<div><br>
</div>
<div><font face="arial, sans-serif">The literature says it was
used until recently by Hamachi <a moz-do-not-send="true"
href="http://en.wikipedia.org/wiki/Hamachi_%28software%29">http://en.wikipedia.org/wiki/Hamachi_(software)</a></font><span
style="font-family:arial,sans-serif">. I am wondering if one
of my colleagues sneaked in a Hamachi server somewhere on the
network that is handing these</span><span
style="font-family:arial,sans-serif"> IP's to the PPTP
clients.</span></div>
</blockquote>
<br>
This is correct. Until IANA ran out of allocations, there were
entire large networks that were not allocated. 1.0.0.0/8 and
5.0.0.0/8 are the ones I remember, though it is interesting that
42.0.0.0/8 was used that way as well. Oops. Bad form on the
vendors that did that; unallocated IP address space is specifically
reserved and must not be used.<br>
<br>
It sounds like the VPN software that you're using learned that this
was at some point used by another vendor for the same purpose and
figured "If they're doing it, why don't we?" and so did so. That be
my guess, anyway.<br>
<br>
Thankfully, there is no need for such things today; we can throw up
organization-scope IPv6 networks and network islands very easily and
there is no need to dig into IPv4 space at all; if you have devices
on that network that are IPv4-only, and it's an island, and you
don't want to use RFC1918 space, then you can always use TEST-NET-1,
TEST-NET-2 and TEST-NET-3, which are more-or-less intended for such
use.<br>
<br>
I would reconfigure that VPN server posthaste, however; the first
time someone gets a link to a DNS name which unexpectedly resolves
to a 5.0.0.0/8 address, Bad Things™ will happen.<br>
<br>
— Mike<br>
<br>
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