Control Messages
| Type | Code | Description |
|---|---|---|
| 0 – Echo Reply | 0 | Echo reply (used to ping) |
| 1 and 2 | Reserved | |
| 3 – Destination Unreachable | 0 | Destination network unreachable |
| 1 | Destination host unreachable | |
| 2 | Destination protocol unreachable | |
| 3 | Destination port unreachable | |
| 4 | Fragmentation required, and DF flag set | |
| 5 | Source route failed | |
| 6 | Destination network unknown | |
| 7 | Destination host unknown | |
| 8 | Source host isolated | |
| 9 | Network administratively prohibited | |
| 10 | Host administratively prohibited | |
| 11 | Network unreachable for TOS | |
| 12 | Host unreachable for TOS | |
| 13 | Communication administratively prohibited | |
| 14 | Host Precedence Violation | |
| 15 | Precedence cutoff in effect | |
| 4 – Source Quench | 0 | Source quench (congestion control) |
| 5 – Redirect Message | 0 | Redirect Datagram for the Network |
| 1 | Redirect Datagram for the Host | |
| 2 | Redirect Datagram for the TOS & network | |
| 3 | Redirect Datagram for the TOS & host | |
| 6 | Alternate Host Address | |
| 7 | Reserved | |
| 8 – Echo Request | 0 | Echo request (used to ping) |
| 9 – Router Advertisement | 0 | Router Advertisement |
| 10 – Router Solicitation | 0 | Router discovery/selection/solicitation |
| 11 – Time Exceeded | 0 | TTL expired in transit |
| 1 | Fragment reassembly time exceeded | |
| 12 – Parameter Problem: Bad IP header | 0 | Pointer indicates the error |
| 1 | Missing a required option | |
| 2 | Bad length | |
| 13 – Timestamp | 0 | Timestamp |
| 14 – Timestamp Reply | 0 | Timestamp reply |
| 15 – Information Request | 0 | Information Request |
| 16 – Information Reply | 0 | Information Reply |
| 17 – Address Mask Request | 0 | Address Mask Request |
| 18 – Address Mask Reply | 0 | Address Mask Reply |
| 19 | Reserved for security | |
| 20 through 29 | Reserved for robustness experiment | |
| 30 – Traceroute | 0 | Information Request |
| 31 | Datagram Conversion Error | |
| 32 | Mobile Host Redirect | |
| 33 | Where-Are-You (originally meant for IPv6) | |
| 34 | Here-I-Am (originally meant for IPv6) | |
| 35 | Mobile Registration Request | |
| 36 | Mobile Registration Reply | |
| 37 | Domain Name Request | |
| 38 | Domain Name Reply | |
| 39 | SKIP Algorithm Discovery Protocol, Simple Key-Management for Internet Protocol | |
| 40 | Photuris, Security failures | |
| 41 | ICMP for experimental mobility protocols such as Seamoby | |
| 42 through 255 | Reserved |
Read more about this topic: ICMP Address Mask Reply
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