Introduction: The Traffic Cop
If you plug an Ethernet cable into your laptop *and* connect to Wi-Fi, you have two active IP addresses on two different interfaces. When you open a webpage, how does the operating system know which interface to use? It checks the IP Route Table.
The 'ip route' Command
If you type ip route in a Linux terminal, it prints the map the kernel uses. It looks for the most 'specific' rule. If there is no specific rule for a destination, it sends the data to the **Default Gateway** (usually your Wi-Fi router). Network admins manipulate this table to force secure traffic out via a VPN interface (`tun0`) and general traffic out via Ethernet (`eth0`).
Conclusion
The routing table is the immediate logic of your computer. It is the final checkpoint before an IP packet leaves the hardware. See your default routing paths here.