When a router cannot route a datagram or host cannot deliver a datagram, the datagram is discarded and the router or the host sends a ____________ message back to the source host that initiated the datagram.
A. Destination unreachable
B. Source quench
C. Router error
D. Time exceeded
Answer:A
When a router cannot route a datagram or host cannot deliver a datagram, the datagram is discarded and the router or the host sends a ____________ message back to the source host that initiated the datagram.
A. Destination unreachable B. Source quench C. Router error D. Time exceeded
Explanation: Router sends destination unreachable message if the destination is not found. Destination unreachable is type 3 error reporting message. It is invoked when the router can’t find a path to the intended destination to forward the packet through.