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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  TCP/IP Routing Protocols (Gateway Protocols)
                9  TCP/IP Interior Routing Protocols (RIP, OSPF, GGP, HELLO, IGRP, EIGRP)
                     9  TCP/IP Routing Information Protocol (RIP, RIP-2 and RIPng)
                          9  RIP Version-Specific Message Formats and Features

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RIP Version 2 (RIP-2) Message Format and Features
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Open Shortest Path First (OSPF)
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RIPng ("RIPv6") Message Format and Features
(Page 3 of 3)

RIPng Message Format

The message format for RIPng is similar to that of RIP-1 and RIP-2, except for the format of the Route Table Entries; it is shown in Table 122 and Figure 178.

Table 122: RIPng Message Format

Field Name

Size (bytes)




Command Type: Identifies the type of RIPng message being sent. A value of 1 indicates an RIPng Request, while 2 means an RIPng Response.



Version Number: Set to 1 (not 6, since this is the first version of the new protocol RIPng.)

Must Be Zero


Reserved: Field reserved; value must be set to all zeroes.

Route Table Entries (RTEs)



Figure 178: RIPng Message Format

RIPng retains the use of Route Table Entries (RTEs) from RIP-2, but their format has been changed to accommodate the much larger IPv6 address size. The limit of 25 entries per message has also been eliminated.


The maximum number of RTEs in RIPng is not restricted to 25 as it is in RIP-1 and RIP-2. It is limited only by the maximum transmission unit (MTU) of the network over which the message is being sent.

Key Concept: RIPng is the version of RIP that was developed for use on IPv6 internetworks. It is technically a distinct protocol from RIP-1 and RIP-2 but is very similar to both. It retains the enhancements to RIP made in RIP-2, making changes to these features and to the RIP message format where needed for compatibility with IPv6.

When a Next Hop needs to be specified, a special RTE is included as I mentioned before. This RTE is included before all the RTEs to which it applies. It has the same basic structure as shown for regular RTEs in Table 122, with the IPv6 Prefix subfield containing the next hop address, the Route Tag and Prefix Len fields set to 0, and the Metric field set to 255 (0xFF).


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