When you need this: Check my network warns about CGNAT, or Tact-VC works on one network but not on another.
Some internet providers, and all mobile hotspots, share one IPv4 address among many customers. This is called CGNAT. Opening or forwarding ports can't help then, because the shared address isn't yours.
What you can do
- Use IPv6. Calls work over IPv6, and with any friend who is reachable. If IPv6 is off in your router's internet settings, turn it on.
- Ask your provider for your own public IPv4 address. Providers call it public IPv4 or dual stack. Many give it on request.
- Both on hotspots or CGNAT? Then both of you need IPv6.
Office, school, hotel and public networks
Some of these networks block direct connections entirely. Tact-VC is made for home networks. On such networks, use your home connection or a mobile hotspot instead.