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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)
                9  ICMP Message Types and Formats
                     9  ICMP Version 4 (ICMPv4) Informational Message Types and Formats

Previous Topic/Section
ICMPv4 Timestamp (Request) and Timestamp Reply Messages
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1
2
34
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ICMPv4 Address Mask Request and Reply Messages
Next Topic/Section

ICMPv4 Router Advertisement and Router Solicitation Messages
(Page 2 of 4)

ICMPv4 Router Advertisement Message Format

The ICMPv4 Router Advertisement message format is shown in Table 98 and Figure 148.


Table 98: ICMPv4 Router Advertisement Message Format

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

 



Figure 148: ICMPv4 Router Advertisement Message Format

 


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ICMPv4 Timestamp (Request) and Timestamp Reply Messages
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Next Page
ICMPv4 Address Mask Request and Reply Messages
Next Topic/Section

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