10 ms·

Its still true though my public IP is 157.x.x.x while behind NAT it's 25.x.x.x 25.x is assigned to UK defence ministry as per the thread. Any ideas?

icedchai 6y ago
25.x.x.x is not advertised globally, not announced with BGP, so they're using it as private IP space. This works because you will never connect to a 25.x.x.x IP. It's just NAT.
- deleted 6y ago
  [deleted]
- p1mrx 6y ago
  > you will never connect to a 25.x.x.x IP Unless the UK decides to sell it. An IPv4 /8 is worth at least $250 million at the moment.
  - icedchai 6y ago
    $250 million is pocket change to a nation state. I own a /24 myself (it's routed), and would never sell it.
    - dylz 6y ago
      When you say owned, do you mean like a PI or legacy allocation?
      - icedchai 6y ago
        Yes, it's a legacy allocation from the early 90's. It predates ARIN.
profmonocle 6y ago
There aren't enough private IPv4 addresses for large(ish) mobile networks to address all their customers devices. Some networks work around this by using public v4 addresses which simply aren't in use. The UK DOD's block has never been publicly advertised (AFAIK) so they decided it was a "safe" block to use for this purpose. This isn't a new practice - I remember seeing Sprint doing this same thing many years ago. The "correct" way to handle this would be to reuse real private IPv4 addresses within your network by segmenting it somehow, or do what some networks have done (T-Mobile US is probably the biggest) - use IPv6 with NAT64. That lets them forego internal IPv4 entirely and only use it at the edge for NAT.
- rohan1024 6y ago
  So if UK DOD chooses to publicly advertise someday my Internet will break. Good to know.
  - api 6y ago
    No, you just would not be able to reach UK DOD.
    - rohan1024 6y ago
      On reconnection got a 56.x ip so USPS as well.
    - lmm 6y ago
      Or whoever they transfer their address space to, if they try to be more socially responsible, which might end up being the next cool startup.
      - api 6y ago
        That would be socially irresponsible. Use IPv6.
      - m01 6y ago
        I suspect major cloud providers may well end up buying the address space if it were to become available, so quite a few companies' services may not be reachable.
c0nsumer 6y ago
I've seen 26.x.x.x get used as well for the same reasons. (US Department of Defense)

icedchai 6y ago

25.x.x.x is not advertised globally, not announced with BGP, so they're using it as private IP space. This works because you will never connect to a 25.x.x.x IP. It's just NAT.

deleted 6y ago
[deleted]
p1mrx 6y ago
> you will never connect to a 25.x.x.x IP Unless the UK decides to sell it. An IPv4 /8 is worth at least $250 million at the moment.
- icedchai 6y ago
  $250 million is pocket change to a nation state. I own a /24 myself (it's routed), and would never sell it.
  - dylz 6y ago
    When you say owned, do you mean like a PI or legacy allocation?
    - icedchai 6y ago
      Yes, it's a legacy allocation from the early 90's. It predates ARIN.

profmonocle 6y ago

There aren't enough private IPv4 addresses for large(ish) mobile networks to address all their customers devices. Some networks work around this by using public v4 addresses which simply aren't in use. The UK DOD's block has never been publicly advertised (AFAIK) so they decided it was a "safe" block to use for this purpose. This isn't a new practice - I remember seeing Sprint doing this same thing many years ago. The "correct" way to handle this would be to reuse real private IPv4 addresses within your network by segmenting it somehow, or do what some networks have done (T-Mobile US is probably the biggest) - use IPv6 with NAT64. That lets them forego internal IPv4 entirely and only use it at the edge for NAT.

rohan1024 6y ago
So if UK DOD chooses to publicly advertise someday my Internet will break. Good to know.
- api 6y ago
  No, you just would not be able to reach UK DOD.
  - rohan1024 6y ago
    On reconnection got a 56.x ip so USPS as well.
  - lmm 6y ago
    Or whoever they transfer their address space to, if they try to be more socially responsible, which might end up being the next cool startup.
    - api 6y ago
      That would be socially irresponsible. Use IPv6.
    - m01 6y ago
      I suspect major cloud providers may well end up buying the address space if it were to become available, so quite a few companies' services may not be reachable.

c0nsumer 6y ago

I've seen 26.x.x.x get used as well for the same reasons. (US Department of Defense)