Field Name

Size (bytes)

Description

Type

1

Type: Identifies the ICMP message type. For Router Advertisement messages the value is 9.

Code

1

Code: Normally set to 0. When a Mobile IP agent is sending a Router Advertisement with an Agent Advertisement extension, it may set the value to 16 if the device is a mobile agent only and doesn’t intend to handle normal traffic. See the discussion of Mobile IP agent discovery for details.

Checksum

2

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

Num Addrs

1

Number Of Addresses: The number of addresses associated with this router that are included in this advertisement.

Addr Entry Size

1

Address Entry Size: The number of 32-bit words of information included with each address. Since in this message format each router address has a 32-bit address and a 32-bit preference level, this value is fixed at 2.

Lifetime

2

Lifetime: The number of seconds that a host should consider the information in this message valid.

Router Address Entries

Value of Num Addrs field * 8