| ICMP (INTERNET CONTROL MESSAGE PROTOCOL) CODES | ||
| Type | Code | Meaning |
| 0 | 0 | ECHO REPLY (ping reply) |
| 3 | DESTINATION UNREACHABLE | |
| 0 | network unreachable | |
| 1 | host unreachable | |
| 2 | protocol unreachable | |
| 3 | port unreachable | |
| 4 | frag needed | |
| 5 | source route failed | |
| 6 | destination network unknown | |
| 7 | destination host unknown | |
| 8 | source host isolated | |
| 9 | destination network administratively prohibited | |
| 10 | destination host administratively prohibited | |
| 11 | network unreachable for TOS | |
| 12 | host unreachable for TOS | |
| 13 | prohibited by filtering | |
| 14 | host precedence violation | |
| 15 | precedence cutoff | |
| 4 | 0 | SOURCE QUENCH |
| 5 | REDIRECT | |
| 0 | network | |
| 1 | host | |
| 2 | network & TOS | |
| 3 | host & TOS | |
| 8 | 0 | ECHO REQUEST (ping request) |
| 9 | 0 | ROUTER ADVERTISEMENT |
| 10 | 0 | ROUTER SOLICITATION |
| 11 | TIME EXCEEDED | |
| 0 | TTL=0 during transmit | |
| 1 | TTL=0 during reassembly | |
| 12 | PARAMETER PROBLEM | |
| 13 | 0 | TIMESTAMP REQUEST |
| 14 | 0 | TIMESTAMP REPLY |
| 15 | 0 | INFO REQUEST |
| 16 | 0 | INFO REPLY |
| 17 | 0 | ADDRESS MASK REQUEST |
| 18 | 0 | ADDRESS MASK REPLY |