default route
also: default gateway, 0.0.0.0/0
The network route used to forward packets when no more specific route matches the destination address. Typically points to a gateway that connects your system to other networks.
A default route is the catch-all route in a system's routing table that handles any network traffic whose destination doesn't match a more specific route. It's identified by the destination 0.0.0.0/0 (for IPv4) or ::/0 (for IPv6), meaning it matches all addresses.
When your Linux system needs to send a packet to a remote host, it checks its routing table from most specific to least specific. If no explicit route exists for that destination, the default route takes over, usually directing traffic through your configured gateway or router.
Example: On a home network, your default route typically points to your WiFi router's IP address (like 192.168.1.1). Any traffic destined outside your local network gets sent there. View your routing table with ip route show or route -n; the line showing default via 192.168.1.1 dev eth0 is your default route.