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ICMP & ICMPv6 Type/Code Reference

Searchable reference of ICMP (IPv4) and ICMPv6 message type and code values, with the ICMPv6 error vs informational split and a type/code lookup.

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Type / code lookup

ICMP and ICMPv6 type and code reference

VersionTypeCodeNameReferenceICMPv6 message class
ICMPv40(type)Echo ReplyRFC 792—
ICMPv43(type)Destination UnreachableRFC 792—
ICMPv430Net UnreachableRFC 792—
ICMPv431Host UnreachableRFC 792—
ICMPv432Protocol UnreachableRFC 792—
ICMPv433Port UnreachableRFC 792—
ICMPv434Fragmentation Needed and Don't Fragment was SetRFC 792, RFC 1191—
ICMPv435Source Route FailedRFC 792—
ICMPv436Destination Network UnknownRFC 1122—
ICMPv437Destination Host UnknownRFC 1122—
ICMPv438Source Host IsolatedRFC 1122—
ICMPv439Communication with Destination Network is Administratively ProhibitedRFC 1122—
ICMPv4310Communication with Destination Host is Administratively ProhibitedRFC 1122—
ICMPv4311Destination Network Unreachable for Type of ServiceRFC 1122—
ICMPv4312Destination Host Unreachable for Type of ServiceRFC 1122—
ICMPv4313Communication Administratively ProhibitedRFC 1812—
ICMPv44(type)Source Quench (deprecated by RFC 6633)RFC 792, RFC 6633—
ICMPv45(type)RedirectRFC 792—
ICMPv450Redirect Datagram for the NetworkRFC 792—
ICMPv451Redirect Datagram for the HostRFC 792—
ICMPv452Redirect Datagram for the Type of Service and NetworkRFC 792—
ICMPv453Redirect Datagram for the Type of Service and HostRFC 792—
ICMPv48(type)Echo RequestRFC 792—
ICMPv49(type)Router AdvertisementRFC 1256—
ICMPv410(type)Router SolicitationRFC 1256—
ICMPv411(type)Time ExceededRFC 792—
ICMPv4110Time to Live Exceeded in TransitRFC 792—
ICMPv4111Fragment Reassembly Time ExceededRFC 792—
ICMPv412(type)Parameter ProblemRFC 792—
ICMPv4120Pointer indicates the errorRFC 792—
ICMPv4121Missing a Required OptionRFC 1108—
ICMPv4122Bad LengthRFC 792—
ICMPv413(type)TimestampRFC 792—
ICMPv414(type)Timestamp ReplyRFC 792—
ICMPv61(type)Destination UnreachableRFC 4443error
ICMPv610No route to destinationRFC 4443error
ICMPv611Communication with destination administratively prohibitedRFC 4443error
ICMPv612Beyond scope of source addressRFC 4443error
ICMPv613Address unreachableRFC 4443error
ICMPv614Port unreachableRFC 4443error
ICMPv615Source address failed ingress/egress policyRFC 4443error
ICMPv616Reject route to destinationRFC 4443error
ICMPv62(type)Packet Too BigRFC 4443error
ICMPv63(type)Time ExceededRFC 4443error
ICMPv630Hop limit exceeded in transitRFC 4443error
ICMPv631Fragment reassembly time exceededRFC 4443error
ICMPv64(type)Parameter ProblemRFC 4443error
ICMPv640Erroneous header field encounteredRFC 4443error
ICMPv641Unrecognized Next Header type encounteredRFC 4443error
ICMPv642Unrecognized IPv6 option encounteredRFC 4443error
ICMPv6128(type)Echo RequestRFC 4443informational
ICMPv6129(type)Echo ReplyRFC 4443informational
ICMPv6130(type)Multicast Listener QueryRFC 2710informational
ICMPv6131(type)Multicast Listener ReportRFC 2710informational
ICMPv6132(type)Multicast Listener DoneRFC 2710informational
ICMPv6133(type)Router SolicitationRFC 4861informational
ICMPv6134(type)Router AdvertisementRFC 4861informational
ICMPv6135(type)Neighbor SolicitationRFC 4861informational
ICMPv6136(type)Neighbor AdvertisementRFC 4861informational
ICMPv6137(type)Redirect MessageRFC 4861informational
ICMPv6143(type)Multicast Listener Discovery Version 2 (MLDv2) ReportRFC 3810informational
How it works

A reference of ICMP for IPv4 (RFC 792, 1122, 1191, 1256, 1812, 6633) and ICMPv6 (RFC 4443, 4861, 2710, 3810) message types and codes. A row with an empty code describes the type itself; a numbered code row describes one code within that type. Type 4 (Source Quench) was deprecated by RFC 6633. In ICMPv6 there is a hard numeric rule: types 1-127 are error messages and types 128-255 are informational messages (RFC 4443); ICMPv4 has no equivalent split. Operational warning: blanket-dropping ICMP breaks Path MTU Discovery — ICMPv4 type 3 code 4 (Fragmentation Needed) and ICMPv6 type 2 (Packet Too Big) — and on IPv6 it breaks Neighbor Discovery (types 133-137); permit at least those rather than filtering ICMP entirely. This is a curated subset of the IANA registries; only entries verified as correct are listed. The full table renders without JavaScript; text filtering and the lookup panel need JavaScript.

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