ICMP message types

ICMPv4 uses different types of messages. ICMP messages are identified by the "Type" field in ICMPv4 header. ICMPv4 header has a "Code" field also. The Type field in ICMPv4 header determines what the ICMP packet is used for. The Code field contains additional information related with Type field.

Following table lists some important ICMPv4 message types.

ICMP Message Type number ICMP Message Type Description
0 and 8 Echo Request/Echo Reply ICMP Echo/Echo Reply type of messages are used by uilities like Ping, Tracert, Pathping etc. These tools are mainly used for network troubleshooting.
3 Destination Unreachable ICMP Destination unreachable type of messages are used by computers or routers to inform the sender that the destination is unreachable. Reason why unreachable also may be included.
4 Source Quench ICMP Source Quench type of messages allows to inform a sending computer to drcrease its sending rate to ease congestion. Deprecated.
5 Redirect ICMP redirect type of messages allows a router on a nonoptimal route between sender and receiver to redirect traffic via a better path.
9 Router Advertisement ICMP Router Advertisement type of messages allows routers to advertise their presence to computers in a network segment. Computers discover the addresses of the routers by listening Router Advertisement messages.
10 Router Solicitation ICMP Router Solicitation type of messages are used by computers in a network segment for immediate Router Advertisement messages.
11 Time Exceeded ICMP Time Exceeded type of messages are used to indicate that the IP datagram’s Time-to-Live (TTL) value value has exceeded or fragment reassmbly timer timed out.
12 Parameter Problem ICMP Parameter Problem message allows to inform thet some error happened while processing the IPv4 datagram.
13 and 14 ICMP Timestamp Request and Timestamp Reply messages ICMP Timestamp Request and Timestamp Reply messages are used by network devices to synchronize their system clock.
40 Photuris ICMP Photuris messages used to communicate messages related with Photuris security protocol.


Following tables shows some ICMP message Type numbers. Please note that some are deprecated and some other are related with IPv6.

ICMP Type number Description Status Related RFC
0 Echo Reply RFC 792
1-2 Unassigned
3 Destination Unreachable RFC 792
4 Source Quench Deprecated RFC 792
5 Redirect RFC 792
6 Alternate Host Address Deprecated
7 Unassigned
8 Echo RFC 792
9 Router Advertisement RFC 1256
10 Router Solicitation RFC 1256
11 Time Exceeded RFC 792
12 Parameter Problem RFC 792
13 Timestamp RFC 792
14 Timestamp Reply RFC 792
15 Information Request Deprecated RFC 792
16 Information Reply Deprecated RFC 792
17 Address Mask Request Deprecated RFC 950
18 Address Mask Reply Deprecated RFC 950
19-29 Reserved
30 Traceroute RFC 1393
31 Datagram Conversion Error Deprecated RFC 1475
32 Mobile Host Redirect Deprecated
33 IPv6 Where-Are-You Deprecated
34 IPv6 I-Am-Here Deprecated
35 Mobile Registration Request Deprecated
36 Mobile Registration Reply Deprecated
37 Domain Name Request Deprecated
38 Domain Name Reply Deprecated
39 SKIP Deprecated
40 Photuris RFC 2521
41 Experimental
42-252 Unassigned
253-254 Reserved RFC 4727


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Introduction to TCP/IP, Features of TCP/IP, TCP/IP History, What is RFC (Request for Comments)
Seven Layers of OSI Model and functions of seven layers of OSI model
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ICMP Echo Request and Echo Reply messages
ICMP Destination Unreachable messages
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ICMP Router Advertisement messages
ICMP Router Solicitation messages
ICMP Time Exceeded messages
ICMP Parameter Problem messages
ICMP Timestamp Request and Timestamp Reply messages
ICMP Photuris messages