ZeroTier Not Working with CSF Firewall Even After Allowing All UDP Traffic

Hello,

I’m experiencing a persistent issue with ZeroTier not working when the CSF (ConfigServer Security & Firewall) is active on my Linux system. Despite extensive attempts to configure the firewall to allow ZeroTier traffic, I’m still encountering connectivity issues.

Here’s what I’ve tried so far:

  1. I have allowed all UDP traffic in both UDP_IN and UDP_OUT sections of my CSF configuration.
  2. I have opened the UDP port 9993, which ZeroTier primarily uses, in both UDP_IN and UDP_OUT sections of my CSF configuration.
  3. I have added specific rules in the csf.allow file to permit all outbound traffic from my server to the port 9993.

Despite these steps, ZeroTier does not work when CSF is active. As soon as I disable CSF, ZeroTier starts working immediately. This issue persists even when all UDP traffic is allowed, suggesting that it’s not just a configuration problem.

I’m seeking guidance on how to configure CSF to allow ZeroTier to function correctly. Is there a specific range of ports that ZeroTier uses for outbound traffic that I could specify in my CSF configuration? Or is there another way to resolve this issue that I might not be aware of?

Any assistance would be greatly appreciated.