Background (Cont.)

• An ICMP message should not be sent in response to:

• • An ICMP error
  • A packet sent to a broadcast or multicast IP address
  • A packet sent to a broadcast or multicast link-layer address
  • A packet with an invalid source address (e.g., 0.0.0.0)
  • Any IP fragment except the first fragment of a packet

• In these cases, the IP packet should be silently discarded