A router receives an incoming packet and cannot determine where to forward it. What will the router do?

When a router receives a packet that it cannot determine where to forward, it typically follows these steps:

1. The router checks its routing table to find a path to the packet's destination IP address. If it cannot find a path, it moves to the next step.

2. The router will then check if it has a default gateway set. A default gateway is a router that it can send packets to if it doesn't know where else to send them. If a default gateway is set, the router will forward the packet to the default gateway.

3. If the router does not have a default gateway set, it will drop the packet. This is because it has no information on where to send the packet.

4. After dropping the packet, the router will typically send an ICMP "Destination Unreachable" message back to the source of the packet. This lets the source know that the packet could not be delivered.

5. The process ends here if the router cannot determine where to forward the packet.