Field Name

Size (bytes)

Description

Type

1

Type: Identifies the ICMPv6 message type; for Router Renumbering messages the value is 138.

Code

1

Checksum

2

Checksum: 16-bit checksum field for the ICMP header, as described in the topic on the ICMP common message format.

Sequence Number

4

Sequence Number: A 32-bit sequence number used to guard against “replay” attacks by allowing a recipient to detect stale, duplicate or “out of order” commands.

Segment Number

1

Segment Number: Differentiates between valid Router Renumbering messages within the same Sequence Number.

Flags

1

Max Delay

2

Maximum Delay: Tells a router receiving a message the maximum amount of time (in milliseconds) it is allowed to delay before sending a reply.

Reserved

4

Reserved: 4 reserved bytes.

Message Body

Variable

Message Body: For a Router Renumbering Command, the message body contains two sets of information. The first is a Match-Prefix Part for the prefix being renumbered. The second is one or more Use-Prefix Parts that describe the new prefix for each match. A router receiving a Command checks its own interface addresses and if they match the Match-Prefix-Part, they use Use-Prefix Parts data to accomplish the renumbering.

For a Router Renumbering Result, the message body contains zero or more Match Results entries that describe each prefix that a router matched from a Router Renumbering Command. Each entry provides information regarding whether renumbering was successful or not for a prefix.