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Some ISPs are resorting to CGNAT eg. https://help.2degreesmobile.co.nz/app/answers/detail/a_id/402/~/changes-to-ip-addresses-%28cgnat%29 https://help.2degreesmo

Some ISPs are resorting to CGNAT eg. https://help.2degreesmobile.co.nz/app/answers/detail/a_id/402/~/changes-to-ip-addresses-%28cgnat%29 https://help.2degreesmobile.co.nz/app/answers/detail/a_id/40...

pkulak 7y ago
Man, that would suck to be behind one of those.
- ripdog 7y ago
  I use 2degrees. They gave me a static public IP for free when I asked and justified it. Most people who just browse Facebook and Instagram, watch YouTube and Netflix won't notice a thing.
- lucb1e 7y ago
  Tell me about it. Rented a place in Amsterdam that came with a Ziggo connection. Wanted to play a game online with someone and I couldn't. No way to host a game. Called support, they said I had a shared ipv4 address. They'd be happy to switch it to a real one but then I'd lose my v6 connection. I didn't know what to tell them. These connections need to come with warning symbols, this isn't what I expect of an Internet connection (I think they deployed "dual-stack lite" but it isn't mentioned in the contract, and even if it is, it should be called "Internet lite"). Still happy with my XS4ALL connection on fiber. Proper /48 subnet and static legacy IPv4 address since ~2011.
  - saurik 7y ago
    Why can't you host a game behind CGNAT? You should be able to use PCP or STUN to establish an incoming port, no?
    - MayeulC 7y ago
      But wouldn't the game itself would have to support something like STUN? AFAIK, it's a handshake between the two ends, made trough a third party server. Both parties need to contact the third party server, then they get an IP:port combination. So you would have to do that, then quickly enter that information in the game client and server, while making sure that the TTL doesn't expire. You might also have to fight your OS a bit. Moreover, STUN doesn't work on symmetrical NAT, where the router uses the incoming address of a packet to route it trough the host. I don't know PCP; I'll look into that. IMO, the solution to the GP's issue is a VPN. Hamachi used to be a popular solution among gamers, I think.
      - saurik 7y ago
        My point was not about the user being able to work around game limitations but to assert that this is, first, a game limitation, wherein it failed to account for the existence of NATs. NATs aren't some new problem: my computer has not had a public routable IP address essentially ever, as even when I was using dial-up in 1995 I had set up a Linux server in our basement to use NAT (as I wanted to have multiple machines in my house always connected). I just don't see why CGNAT is somehow bad or worse or even different than NAT, if the game supports NATs (which it sounds like in your case it doesn't). Yes: "symmetric NAT" is useless, but I have not yet seen a CGNAT deployment use symmetric NAT. I would just go so far as to say "symmetric NAT is an example of a technology that is not and never will be good enough to be called carrier grade" ;P. So like, that NAT can and has sucked shouldn't be a demonstration that all NAT everywhere is entirely useless. It could very well be that CGNAT deployments don't have support for PCP, (or the related NAT-PMP and UPnP mechanisms that it is a successor to), which would suck. I haven't checked this yet. However, if they do, you should be able to do just about anything you could on any private NAT setup: these protocols let you ask your NAT to open a reverse port mapping to your system on a routable IP address, and you can use them with external tooling (they don't require you to be inside the app listening on the port or anything).

pkulak 7y ago

Man, that would suck to be behind one of those.

ripdog 7y ago
I use 2degrees. They gave me a static public IP for free when I asked and justified it. Most people who just browse Facebook and Instagram, watch YouTube and Netflix won't notice a thing.
lucb1e 7y ago
Tell me about it. Rented a place in Amsterdam that came with a Ziggo connection. Wanted to play a game online with someone and I couldn't. No way to host a game. Called support, they said I had a shared ipv4 address. They'd be happy to switch it to a real one but then I'd lose my v6 connection. I didn't know what to tell them. These connections need to come with warning symbols, this isn't what I expect of an Internet connection (I think they deployed "dual-stack lite" but it isn't mentioned in the contract, and even if it is, it should be called "Internet lite"). Still happy with my XS4ALL connection on fiber. Proper /48 subnet and static legacy IPv4 address since ~2011.
- saurik 7y ago
  Why can't you host a game behind CGNAT? You should be able to use PCP or STUN to establish an incoming port, no?
  - MayeulC 7y ago
    But wouldn't the game itself would have to support something like STUN? AFAIK, it's a handshake between the two ends, made trough a third party server. Both parties need to contact the third party server, then they get an IP:port combination. So you would have to do that, then quickly enter that information in the game client and server, while making sure that the TTL doesn't expire. You might also have to fight your OS a bit. Moreover, STUN doesn't work on symmetrical NAT, where the router uses the incoming address of a packet to route it trough the host. I don't know PCP; I'll look into that. IMO, the solution to the GP's issue is a VPN. Hamachi used to be a popular solution among gamers, I think.
    - saurik 7y ago
      My point was not about the user being able to work around game limitations but to assert that this is, first, a game limitation, wherein it failed to account for the existence of NATs. NATs aren't some new problem: my computer has not had a public routable IP address essentially ever, as even when I was using dial-up in 1995 I had set up a Linux server in our basement to use NAT (as I wanted to have multiple machines in my house always connected). I just don't see why CGNAT is somehow bad or worse or even different than NAT, if the game supports NATs (which it sounds like in your case it doesn't). Yes: "symmetric NAT" is useless, but I have not yet seen a CGNAT deployment use symmetric NAT. I would just go so far as to say "symmetric NAT is an example of a technology that is not and never will be good enough to be called carrier grade" ;P. So like, that NAT can and has sucked shouldn't be a demonstration that all NAT everywhere is entirely useless. It could very well be that CGNAT deployments don't have support for PCP, (or the related NAT-PMP and UPnP mechanisms that it is a successor to), which would suck. I haven't checked this yet. However, if they do, you should be able to do just about anything you could on any private NAT setup: these protocols let you ask your NAT to open a reverse port mapping to your system on a routable IP address, and you can use them with external tooling (they don't require you to be inside the app listening on the port or anything).