Static Routing and Distance Vector Routing Protocols - CCIE Routing and Switching Exam Certification Guide - page 330

As in RIPv1, RIPv2 also summarizes IP networks at network boundaries. You can disable
autosummarization with the no auto-summary command, as follows:

router rip
version 2
no auto-summary
You can use RIPv2 in small networks where VLSM is required. You can use authentication to
prevent communication with any RIP routers that are not intended to be part of the network,
such as UNIX stations running routed. Only those RIP updates with the authentication pass-
word are accepted. RFC 1723 defines simple plain text authentication for RIPv2. Besides plain
text passwords, Cisco's implementation provides the ability to use MD5 authentication. MD5
is the message-digest algorithm defined in RFC 1321. Its algorithm takes as input a message of
arbitrary length and produces as output a 128-bit fingerprint or message digest of the input,
making it much more secure than plain text passwords.

RIPv2 Forwarding Information Base
RIPv2 maintains a routing table database, as in version 1. The difference is that the subnet mask
information is also kept. The table information of RIPv1 is repeated here as follows:
•

IP address —IP address of the destination host or network, with subnet mask.

•

Gateway —The first gateway along the path to the destination.

•

Interface —The physical network that you must use to reach the destination.

•

Metric —A number that indicates the number of hops to the destination.

•

Timer —The amount of time since the route entry was last updated.

RIPv2 Message Format
The RIPv2 message format takes advantage of the unused fields in the RIPv1 message format
by adding subnet masks and other information. Figure 7-3 shows the RIPv2 message format.