Describe the role of a default gateway in a routing table.

What will be an ideal response?

Default gateway acts like a “last resort” routing entry in the routing table. When the datagram destination can not be delivered directly (i.e. not within same subnet) and there is no explicit route in the routing table to the network prefix (or the exact IP address) of that destination, datagrams to this destination will be sent to the default gateway for delivery.