Static Routing and Distance Vector Routing Protocols - CCIE Routing and Switching Exam Certification Guide - page 331

RIPv2 Message Format Figure 7-3

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

Command Version Unused (must be zero)

Address Family Identifier Route Tag

IP address (1 st route entry)
Subnet Mask
Next Hop
Metric

Address Family Identified Route Tag

IP address (2 nd route entry up to 25)

Subnet Mask
Next Hop

Metric

The following is a description of each field:
•

Command —Indicates whether the packet is a request or a response message. The request
message asks that a router send all or part of its routing table. Response messages contain
route entries. The response message is set periodically, or as a reply to a request.

•

Version —Specifies the RIP version. It is set to 2 for RIPv2 and 1 for RIPv1.

•

Address Family Identifier —Specifies the address family. RIP is designed to carry
routing information for several different protocols. Each entry has an address-family
identifier to indicate the type of address specified. The address family identifier for IP
is 2. The AFI is set to 0xFFF for the first entry to indicate that the remainder of the entry
contains authentication information.

•

Route Tag —Provides a method for distinguishing between internal routes (learned
by RIP) and external routes (learned from other protocols). Route tags are covered in
Chapter 10.

•

IP address —Specifies the IP address (network) of the destination.