TUN mode, system proxy mode, and transparent proxy mode route traffic differently. Understanding them helps troubleshoot apps bypassing proxy, DNS leaks, and IP mismatch issues.
Quick answer: TUN mode captures traffic through a virtual network interface, system proxy mode only affects apps that honor proxy settings, and transparent proxy mode usually works at the router or gateway layer.
When one app uses the VPN but another does not, the issue is often not the server. It may be the traffic capture mode. TUN mode, system proxy mode, and transparent proxy mode cover different parts of the device or network.
Mode comparison
| Mode | Traffic entry | Best use |
|---|---|---|
| TUN mode | Virtual interface or system VPN tunnel | Device-wide routing and rule-based proxying |
| System proxy | HTTP or SOCKS proxy settings | Browsers and apps that honor proxy settings |
| Transparent proxy | Router, gateway, or firewall redirection | Whole-home or device-without-client scenarios |
Why apps bypass the proxy
- Some apps ignore system proxy settings.
- Per-app routing or split tunneling excludes the target app.
- DNS traffic is not handled by the same route.
- Transparent proxy firewall rules do not match the destination.
How to troubleshoot
- Identify which mode the client is using.
- Test a browser, the target app, and an IP check page separately.
- Switch to global mode temporarily to test rule mismatch.
- Run DNS and WebRTC checks after each change.
- If using a router, compare with a device-side VPN client.
Common questions
Is TUN mode always better?
No. It covers more traffic, but it also depends on system permissions, DNS behavior, and battery policies.
Is transparent proxy beginner-friendly?
Usually not. It is powerful, but a wrong router rule can affect the whole network.
Why does DNS matter here?
DNS may follow a different path from application traffic, causing leaks or incorrect routing decisions.
Related technical guides
- DNS leak test guide
- VPN connected but IP not changing
- Mobile VPN keeps disconnecting
- VPN Kill Switch explained
- Proxy vs VPN comparison