Section B.6. ICMPv6 Message Types and Code Values (Chapter 4, RFC 2463)


B.6. ICMPv6 Message Types and Code Values (Chapter 4, RFC 2463)

Table B-7 provides an overview of the ICMPv6 error message types, along with the additional code information, which depends on the message type.

Table B-7. ICMPv6 error messages and code type

Message number

Message type

Code field

1

Destination Unreachable

0 = no route to destination

1 = communication with destination administratively prohibited

2 = beyond scope of Source address

3 = address unreachable

4 = port unreachable

5 = Source address failed ingress/egress policy

6 = reject route to destination

2

Packet Too Big

Code field set to 0 by the sender and ignored by the receiver

3

Time Exceeded

0 = hop limit exceeded in transit

1 = fragment reassembly time exceeded

4

Parameter Problem

0 = erroneous header field encountered

1 = unrecognized next header type encountered

2 = unrecognized IPv6 option encountered

The pointer field identifies the octet offset within the invoking packet where the error was detected. The pointer points beyond the end of the ICMPv6 packet if the field in error is beyond what can fit in the maximum size of an ICMPv6 error message.

100 and 101

Private experimentation

RFC 4443

127

Reserved for expansion of ICMPv6 error messages

RFC 4443


Table B-8 provides an overview of the ICMPv6 informational messages.

Table B-8. ICMPv6 informational messages

Message number

Message type

Description

128

Echo Request

RFC 4443. Used for the ping command.

129

Echo Reply

 

130

Multicast Listener Query

RFC 2710. Used for multicast goup management.

131

Multicast Listener Report

 

132

Multicast Listener Done

 

133

Router Solicitation

RFC 2461. Used for neighbor discovery and autoconfiguration.

134

Router Advertisement

 

135

Neighbor Solicitation

 

136

Neighbor Advertisement

 

137

Redirect Message

 

138

Router Renumbering

RFC 2894

Codes:

0 = Router renumbering command

1 = Router renumbering result

255 = Sequence number reset

139

ICMP Node Information Query

draft-ietf-ipngwg-icmp-name-lookups-15.txt

140

ICMP Node Information Response

 

141

Inverse ND Solicitation

RFC 3122

142

Inverse ND Adv Message

RFC 3122

143

Version 2 Multicast Listener Report

RFC 3810

144

ICMP Home Agent Address Discovery Request Message

RFC 3775 ICMPv6 Messages for Mobile IPv6

145

ICMP Home Agent Address Discovery Reply Message

 

146

ICMP Mobile Prefix Solicitation Message

 

147

ICMP Mobile Prefix Advertisement Message

 

148

Certification Path Solicitation Message

RFC 3971 ICMPv6 Messages for SEcure Neighbor Discovery

149

Certification Path Advertisement Message

 

151

Multicast Router Advertisement

RFC 4286

152

Multicast Router Solicitation

 

153

Multicast Router Termination

 

200

201

Private experimentation

RFC 4443

255

Reserved for expansion of ICMPv6 informational messages

RFC 4443


Table B-9 lists the possible code values of the Destination Unreachable message (type 1).

Table B-9. Code values of the Destination Unreachable message (type 1)

Code

Description

0

"No route to destination."

This code is used if a router cannot forward a packet because it does not have a route in its table for a destination network. This can happen only if the router does not have an entry for a default route.

1

"Communication with destination administratively prohibited."

This type of message can, for example, be sent by a firewall that cannot forward a packet to a host inside the firewall because of a packet filter. It might also be sent if a node is configured not to accept unauthenticated Echo Requests.

2

"Beyond scope of Source address."

This code is used if the Destination address is beyond the scope of the Source address, e.g., if a packet has a link-local Source address and a global Destination address.

3

"Address unreachable."

This code is used if a Destination address cannot be resolved into a corresponding network address or if there is a data-link layer problem preventing the node from reaching the destination network.

4

"Port unreachable."

This code is used if the transport protocol (e.g., UDP) has no listener and there is no other means to inform the sender. For example, if a Domain Name System (DNS) query is sent to a host and the DNS server is not running, this type of message is generated.

5

"Source address failed ingress/egress policy."

This code is used if a packet with this Source address is not allowed due to ingress or egress filtering policies.

6

"Reject route to destination."

This code is used if the route to the destination is a reject route.


Table B-10 shows the Code fields for the Time Exceeded message.

Table B-10. Code values for Time Exceeded message (type 3)

Code

Description

0

"Hop limit exceeded in transit."

Possible causes: the initial hop limit value is too low; there are routing loops; or use of the traceroute utility.

1

"Fragment reassembly time exceeded."

If a fragmented packet is sent by using a fragment header (refer to Chapter 2 for more details) and the receiving host cannot reassemble all packets within a certain time, it notifies the sender by issuing this ICMP message.


Table B-11 shows the Code fields for the Parameter Problem message.

Table B-11. Code values for Parameter Problem (type 4)

Code

Description

0

Erroneous header field encountered

1

Unrecognized next header type encountered

2

Unrecognized IPv6 option encountered


Table B-12 shows an overview of the different Neighbor Discovery options and the message types in which they are used.

Table B-12. Overview of ND options

Option type

Used in

Type 1

Source link-layer address

Neighbor solicitation

Router solicitation

Router advertisement

IND solicitation/advertisement

Type 2

Target link layer address

Neighbor advertisement

Redirect

IND solicitation/advertisement

Type 3

Prefix

Router advertisement

Type 4

Redirected header

Redirect

Type 5

MTU

Router advertisement

IND solicitation/advertisement

Type 7

Advertisement interval

Router advertisement (defined in Mobile IPv6 specification)

Type 8

Home Agent information

Router advertisement (defined in Mobile IPv6 specification)

Type 9

Source address list

IND Solicitation

Type 10

Target address list

IND Advertisement


A Neighbor Cache entry can be in one of five states according to RFC 2461. The five states are explained in Table B-13.

Table B-13. States of Neighbor Cache entries

State

Description

Incomplete

Address resolution is currently being performed and awaiting either a response or a timeout. Specifically, a Neighbor Solicitation has been sent to the solicited-node multicast address of the target, but the corresponding Neighbor Advertisement has not yet been received.

Reachable

This neighbor is currently reachable, which means positive confirmation was received within the last ReachableTime milliseconds that the neighbor was functioning properly.

Stale

More than ReachableTime milliseconds have elapsed since the last positive confirmation that the forward path was functioning properly was received. No action will take place regarding this neighbor until a packet is sent.

Delay

This neighbor's Reachable Time has expired, and a packet was sent within the last DelayFirstProbeTime seconds. If no confirmation is received within the DelayFirstProbeTime seconds, send a Neighbor Solicitation and change the neighbor state to Probe state.

The use of Delay allows upper-layer protocols additional time to provide reachability confirmation. Without this extra time, possible redundant traffic would be generated.

Probe

A reachability confirmation is being actively attempted by sending Neighbor Solicitations every RetransTimer milliseconds until reachability is confirmed.




IPv6 Essentials
IPv6 Essentials
ISBN: 0596100582
EAN: 2147483647
Year: 2004
Pages: 156
Authors: Silvia Hagen

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