Updated: 07/20/2017 by Computer Hope

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.

Note: With the different IP versions there are two different types of ICMP versions, ICMPv4 for IPv4 and ICMPv6 for IPv6.

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
0 Echo Reply
3 Destination Unreachable
4 Source Quench
5 Redirect Message
8 Echo Request
11 Time Exceeded
12 Parameter Problem
13 Timestamp Request
14 Timestamp Reply
15 Information Request (No Longer Used)
16 Information Reply (No Longer Used)
17 Address Mask Request
18 Address Mask Reply

RFC, Network terms, Protocol, Traceroute