What happens when a router receives a packet for forwarding with a TTL value of...

When a router, such as a FortiGate, receives a packet with a TTL (Time to Live) of 1, it decrements the TTL to 0, drops the packet, and sends an ICMP Time Exceeded message to the source IP. This prevents infinite loops in routing. Option A is incorrect as TTL is decremented, not incremented; B and D are incorrect as the packet is not forwarded when TTL reaches 0. Exact extract: "When a packet’s TTL reaches 1, the router decrements it to 0, drops the packet, and sends an ICMP Time Exceeded message to the source IP address to prevent routing loops."