What is a default gateway?
Why Interviewers Ask This
This is a classic screening question for Networking roles. Hiring managers ask it early in interviews to gauge your baseline understanding and determine if you can communicate technical concepts clearly.
Answer
The default gateway is the router that a device sends packets to when the destination IP address is not on the local network. It is the "exit door" of the local network — the device uses its subnet mask to determine if the destination is local or not. If not local, it forwards the packet to the default gateway, which then routes it toward the destination. In a typical home network, the default gateway is the router's IP address (commonly 192.168.1.1 or 192.168.0.1). When no default gateway is configured, a device can only communicate with other devices on its local subnet. The default gateway must be on the same subnet as the device using it. Check your default gateway: route print (Windows), ip route (Linux), netstat -rn (macOS/Linux).
Common Mistake
Many candidates answer correctly but can't explain the 'why'. Always be prepared to justify your answer with a concrete example or use case from your Networking experience.