2009 Mar 07
| 16 bit - ??? | 16 bit - ??? |
| 16 bit - ??? | 16 bit - ??? |
| ... Data (if any) ... |
|
| Value in the ICMP Type Field |
ICMP Message Type |
Description |
|---|---|---|
| 0 | Echo Reply | Used to respond to a ping when a system is active |
| 3 | Destination Unreachable |
Indicates an earlier IP message could not be delivered to its destination. Could be because a router along the way does not have a know path to the destination, or the destination machine may not know the protocol being used, or the port was closed. |
| 4 | Source Quench |
When a system is receiving packets too fast to process them from its incoming queue, it may send back a Source Quench message to tell the sender to slow down. |
| 5 | Redirect | A router sends this message to indicate that traffic should be directed to another router, which can deliver the traffic to the destination more effeciently. |
| 8 | Echo | Used to send a ping to determine if a system is up. |
| 11 | Time Exceeded |
Indicates that the maximum number of hops in the Time-To-Live field of the IP header was exceeded. |
| 12 | Parameter Problem |
Sent in response to an IP packet with a bad parameter in the header. |
| 13 | Timestamp | Includes the time on the sending machine and requests the time on the destination machine. |
| 14 | Timestamp Reply |
Response to above ICMP packet including time. |
| 15 | Information Request |
Used by a machine to determine which network it is on. |
| 16 | Information Reply |
Response to Information Request message giving netwrok IP address. |
2005-2009