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No one can establish connections from the Internet to my computers anymore because my ISP started using a symmetric NAT a couple of days ago. There wasn't any problem before, I could initiate a connection from the internet to my computers and if a server application was running on some of those computers, a connection could be established because I have port forwarding configured correctly in my router. Now, the packets can't reach my router at all.

What changes I noticed:

-The public IPv4 address which I can see on google or an IP whois site is different than the one which is set on my router's link to my ISP (my router's "WAN" link). I checked the router "WAN" interface's IP address through the router's web interface page (It's a simple home TPLink router).

-My ISP changes the source port numbers of packets that originate from my computers. For ex. a client application is bound to port number 50000 udp. My router sends out the packets with a source port number 50000. My ISP changes this source port number to an arbitrary source port number (for ex. 13418).

Problems

1) If I have a server application running on my computers I cannot send data to it from the Internet because the port isn't open on my ISP's symmetric NAT. For ex. the server listens on port 30000 on one of my computers. That port isn't open on the symmetric NAT of my ISP and if I try to send data from the Internet, the packets cannot reach my router.

2) I use an application called Voobly for gaming - Age of Empires 2 mostly. The way the connections work are: You set a listen port for the Voobly client (for example udp 16000). That port is given by Voobly to other players to establish direct connections to me. So my Voobly client sends udp packets with source port 16000, my TPLink router does NAT and keeps the udp source port 16000, but when the packets try to leave my ISP's network they change the source port to something like 13000. So I'm screwed, UDP hole punching is very hard to achieve and I am having trouble connecting even to people who live in countries next to mine.

Conclusion

I know this is a desperate attempt. I am unable to do anything about it (except maybe change ISPs). I am hoping for a miracle here. Thanks, in advance, to anyone who gives me some information.

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  • There isn't a workaround for your problem.
    – Ramhound
    Feb 23, 2017 at 19:42
  • I know... FeelsBadMan
    – ThePraetor
    Feb 23, 2017 at 19:44
  • 1
    Is there an actual question you have for us? As is, you're just telling us about your situation, and then requesting "some information"...? Regardless, what @ramhound says is correct; you can't control your ISP's network so speak with them to find a solution, and/or switch ISPs. Feb 23, 2017 at 20:03
  • Your ISP probably has no choice. IPv4 addresses have run out so they might need to use NAT to be able to connect their growing customer base. Feb 23, 2017 at 22:08
  • You could be right, but I think they are just greedy and not want to enable regular people to connect their own servers without paying for a static ip address. But there are like 1% of people who actually know how to do this and 0.001% who are actually doing it, at least in my region, still human greed is strong
    – ThePraetor
    Feb 23, 2017 at 22:16

2 Answers 2

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I think the only way to get around this is to use a VPN that gives you a public IP address. If none of the commercially available VPN services do this (I've no idea), then you could rent a virtual private server (VPS) and establish a VPN to that. Not sure it will help with latency of online games though.

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I think you can only use VPS and setup a vpn server on your vps.

And then setup a port forwarding on VPS. Or simply use ssh reverse tunnel to your VPS.

Your description doesn't sound like symmetric NAT. Cone NAT also change your port.

Symmetric NAT means if you connect to different server, NAT will change your port to different random port. If your ISP use Cone NAT, when you connect to different server, your source port will change to random, but same port.

I think email to your ISP is the simplest way.

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