If you are having problems with direct connectivity or with connections being slow or unreliable, try these recommendations:
- Enable IPv6 on your network if it is available.
- Avoid multple layers of NAT, such as plugging NAT routers into the LAN ports of NAT routers. If you are running virtual machines try bridging their network devices directly to your LAN instead of using host-based networking to eliminate a layer of NAT. Multiple layers of NAT introduce instabilities in many protocols due to interactions between different overlapping timeouts and remapping schemes.
- Ensure that your firewall (or AWS/Azure/Google Cloud rules) allows UDP traffic to/from port 9993 at a minimum. Allowing outbound UDP to all ports or to all ports above 9000 is also recommended.
- Check local firewall and security software, especially third party software like McAfee or Little Snitch.
- Enable uPnP and/or NAT-PMP if your router/firewall supports it.
- Check to ensure that a local firewall is not blocking traffic to/from your ZeroTier network(s). Networks you join appear on your computer as additional network devices and local firewalls may apply policies to them. Sometimes the default policy is "untrusted" or "public" which may prohibit most traffic. This is a frequent cause of "I can't ping" problems.