Short for Internet Control Message Protocol, ICMP is an extension to the Internet Protocol defined by RFC 792 and an error reporting protocol for TCP/IP messages. Most users are familiar with ICMP from using the ping command.
ICMP is used by computers and by all types of network devices, including network routers, which help identify problems and communicate the status of devices on the network. The ICMP message contains a TYPE, CODE, and CHECKSUM message that help identify a devices response. The chart below shows a listing of the defined types and their descriptions.
|ICMP TYPE||ICMP Description|
|15||Information request (no longer used).|
|16||Information reply (no longer used).|
|17||Address mask request.|
|18||Address mask reply.|