IP Routing

Destination Unreachable Message

1

0 - No route to destination

1 - Communication with the destination is administratively prohibited, such as a firewall filter

2 - Not assigned

3 - Address unreachable

4 - Port unreachable

A Destination Unreachable message (Type 1) is generated in response to a packet that can not be delivered to its destination address for reasons other than congestion. The reasons for the non-delivery of a packet is described by code field value. For details of all codes, refer to RFC 2463 Section 3.1.

Packet Too Big Message

2

0

A Packet Too Big message is sent in response to a packet that it cannot forward because the packet is larger than the Maximum Transmission Unit (MTU) of the outgoing link.

Time Exceeded Message

3

0 - Hop limit exceeded in transit

1 - Fragment reassembly time exceeded

If a router receives a packet with a hop limit of zero, or a router decrements a packet's hop limit to zero, it must discard the packet and send an ICMPv6 Time Exceeded message with Code 0 to the source of the packet. This indicates either a routing loop or an initial hop limit value that is too small. For more details refer to RFC 2463 section 3.3.

Parameter Problem Message

4

0 - Erroneous header field encountered

1 - Unrecognized next header type encountered

2 - Unrecognized IPv6 option encountered

A Parameter Problem message is generated in response to an IPv6 packet with problem in its IPv6 header, or extension headers, such the node cannot process the packet and must discard it. For more details refer to RFC 2463 section 3.4.

Echo Request Message

128

0

Used to check and troubleshoot connectivity using the IPv6 ping command.

Echo Reply Message

129

0

This message is generated in response to an echo request message.

Router Solicitation Message

133

0

Hosts send router solicitations messages in order to prompt routers to generate router advertisements messages quickly.

Router Advertisement Message

134

0

Routers send out router advertisement message periodically, or in response to a router solicitation.

Neighbor Solicitation Message

135

0

Nodes send neighbor solicitations to request the link-layer address of a target node while also providing their own link-layer address to the target.

Neighbor Advertisement Message

136

0

A node sends neighbor advertisements in response to neighbor solicitations and sends unsolicited neighbor advertisements in order to propagate new information quickly (which is unreliable).

Redirect Message

137

0

Routers send redirect packets to inform a host of a better first-hop node on the path to a destination. Hosts can be redirected to a better first-hop router but can also be informed by a redirect that the destination is in fact a neighbor. The latter is accomplished by setting the ICMP target address equal to the ICMP destination address.

Source Link-Layer Address

1

The Source Link-Layer Address option contains the link-layer address of the sender of the packet. It is used in the neighbor solicitation, router solicitation, and router advertisement packets.

Target Link-Layer Address

2

The Target Link-Layer Address option contains the link-layer address of the target. It is used in neighbor advertisement and redirect packets.

Prefix Information

3

The Prefix Information option provide hosts with on-link prefixes and prefixes for address autoconfiguration.

Redirect Header

4

The Redirected Header option is used in redirect messages and contains all or part of the packet that is being redirected.

MTU

5

The MTU option is used in router advertisement messages to insure that all nodes on a link use the same MTU value in those cases where the link MTU is not well known.