Tunnel with firewall

You can implement a positive security model with Cloudflare Tunnel by blocking all ingress traffic and allowing only egress traffic from cloudflared. Only the services specified in your tunnel configuration will be exposed to the outside world.

​​ Ports

The parameters below can be configured for egress traffic inside of a firewall.

​​ Required for tunnel operation

cloudflared connects to Cloudflare’s global network on port 7844. To use Cloudflare Tunnel, your firewall must allow outbound connections to the following destinations on port 7844 (via UDP if using the quic protocol or TCP if using the http2 protocol).

¹ This rule is only required for firewalls that enforce SNI.

​​ Optional

Opening port 443 enables some optional features. Failure to allow these connections may prompt a log error, but cloudflared will still run correctly.

​​ Firewall configuration

​​ Cloud VM firewall

If you host your services on a virtual machine (VM) instance in a cloud provider, you may set up instance-level firewall rules to block all ingress traffic and allow only egress traffic. For example, on Google Cloud Platform (GCP), you may delete all ingress rules, leaving only the relevant egress rules. This is because GCP’s firewall denies ingress traffic unless it matches an explicit rule.

​​ OS firewall

Alternatively, you may use operating system (OS)-level firewall rules to block all ingress traffic and allow only egress traffic. For example, if your server runs on Linux, you may use iptables to set up firewall rules:

1. Check your current firewall rules.

2. Allow localhost to communicate with itself.

3. Allow already established connection and related traffic.

4. Allow new SSH connections.

5. Drop all other ingress traffic.

6. After setting the firewall rules, use this command to check the current iptables settings:

Run your tunnel and check that all configured services are still accessible to the outside world via the tunnel, but not via the external IP address of the server.

You can also secure your application with Cloudflare Access.

​​ Test connectivity

​​ Test with dig

To test your connectivity to Cloudflare, you can use the dig command to query the hostnames listed above. Note that cloudflared defaults to connecting with IPv4.

​​ Test with PowerShell

On Windows, you can use PowerShell commands if dig is not available.

To test DNS:

To test ports: