Understanding VPN Routing
How routing tables, tunnels and network rules work together.
What is VPN routing?
A VPN creates a path between networks, but routing rules determine which traffic actually uses that path.
Routing Table
The routing table determines where packets are sent and which interface should handle them.
VPN Tunnel
A tunnel provides a virtual path through another network or server.
Routing Rules
Additional rules can select specific traffic and send it through a particular routing table or tunnel.
How the pieces fit together
A simple VPN routing model.
01 — Traffic
A device generates network traffic destined for an Internet service or remote network.
02 — Decision
The operating system checks routing rules and determines the appropriate route.
03 — Tunnel
If the traffic matches the VPN rules, it is sent through the VPN interface.
Common problems
When VPN routing does not work, check the basics first.
Wrong Route
The traffic may still be using the normal WAN interface.
DNS
DNS requests may follow a different path from ordinary application traffic.
Firewall
Firewall and packet-marking rules can prevent traffic from reaching the intended tunnel.