I came across this article and I'm trying to understand what is going on here, I found some packets on my network containing and IP range and It's based on:


It is owned by DoD, is this space routable?


Can an expert explain to me why someone is using this range internally and what the consequences would be?

  • 7
    One of the contracts I maintain does this. I've advised against it, and they are in process of moving away from it, but basically what their logic is, is that the public IP addresses they're using as private blocks belong to a government agency in a state they are 100% certain they'll never need to interact with, and feel it's safe (enough) to use those IP addresses internally. While they're technically right, it's just a bad practice and should be avoided unless absolutely no other option is available.
    – Jesse P.
    Commented Mar 14, 2019 at 16:02
  • They route the network over BGP internally but they aren't advertising it publicly so there's no harm outside of this contract's network (as long as nobody else on the MPLS cloud needs to access the rightful owner of that IP address space, either).
    – Jesse P.
    Commented Mar 14, 2019 at 16:04
  • My company uses real public IPs internally and NATs them at the local office internet routers. It feels wasteful, but saves on VPN problems where you might have a 192.168.x.x network in multiple places and have to fiddle with netmasks to get to the right one. Yes these IPs are allocated to my employer.
    – Criggie
    Commented Mar 14, 2019 at 20:42

2 Answers 2


IPv4 address space is in short supply, so some people decide to use IP space ( allocated, but not advertised) that doesn't belong to them. The consequences are pretty well described in the article you quote.

  • You are saying they are using that range behind their NAT gateway as a private range ( like rfc1918)?
    – Satish
    Commented Mar 14, 2019 at 15:32
  • 7
    @Satish, yes. The problem is that the space will probably start being used at some point, then the users will never be able to access Internet addresses in that space. We acquired a company that used squat space that is now advertised on the Internet, and we had to scramble to change the addressing.
    – Ron Maupin
    Commented Mar 14, 2019 at 17:06

What is IP squat space

Space that someone uses to number their networks even though it is either allocated to someone else or may be allocated to someone else in the future.

"squat space" is generally not routed on the public internet by the squatter. Doing so would be considered a hijack which is a much more serious matter. Instead it is generally used behind a network address translator or for stuff that doesn't need to communicate directly with the Internet.

In the past if an unallocated range was widely squatted on the allocation authorities would hold back on making allocations from that block. However with the IPv4 address crunch this is no longer possible.

It is owned by DoD, is this space routable?

It is routable on the public Internet if the DoD wants to, but as far as I can tell it is not currently routed on the public Internet.

There is a graph showing how much of each /8 is advertised at https://ipv4.potaroo.net/fig05.png , unfortunately it's a bit tricky to interpret because some of the strips seem to be two pixels wide and others three but it doesn't look like any addresses from those blocks are advertised on the internet.

Can an expert explain to me why someone is using this range internally

Some organizations run out of private space internally, either because they weren't stingy enough with their internal allocation policies or because they are just so freaking big that private space doesn't cover their needs.

Others just do it out of ignorance, they don't understand how IP addressing works, so they just make something up.

Still others squat because they are trying to avoid their private network conflicting with customers private networks. This often comes up with things like VPN services.

and what the consequences would be?

It means that if/when the legitimate owners of that IP space start using it on the Internet their services will be unreachable for the squatter and the squatters customers.

I ran into this for a while with a server I run. The server has an address in which was widely squatted on in the past. Notably by Hamachi and by T-Mobile USA. Things did seem to improve over time, Hamachi moved to squatting on a different network, I'm not 100% sure what happened on the T-Mobile side but I stopped seeing complaints coming from there so presumably they did something.

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