Default Gateway
The router address a host sends traffic to when the destination is outside its local subnet.
A default gateway is the IP address of the router interface on the local subnet that a host forwards packets to when the destination falls outside that subnet. The host ANDs the destination address with its own subnet mask; any non-matching traffic is sent to the gateway rather than delivered directly on the local segment. On the N10-009 exam, distinguish the default gateway (a host-side IP setting) from a default route (0.0.0.0/0, a router-side forwarding entry). A misconfigured or missing gateway lets a host reach local devices normally but blocks all inter-network traffic — a classic troubleshooting isolation point.
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