Information Technology Reference
In-Depth Information
RIPv2 and RIPng
This section covers RIPv2 and RIPng. RIPv2 is used for IPv4 networks and RIPng was cre-
ated to support IPv6 networks. RIPv2 was first described in RFC 1388 and RFC 1723
(1994); the current RFC is 2453, written in November 1998. Although current environments
use advanced routing protocols such as OSPF and EIGRP, some networks still use RIP. The
need to use VLSMs and other requirements prompted the definition of RIPv2. RIPv1 was
the first version of RIP, which did not support VLSMs. RIPv1 is not a CCDA topic.
RIPv2 improves on RIPv1 with the ability to use VLSM, with support for route authenti-
cation, and with multicasting of route updates. RIPv2 supports CIDR. It still sends up-
dates every 30 seconds and retains the 15-hop limit; it also uses triggered updates. RIPv2
still uses UDP port 520; the RIP process is responsible for checking the version number. It
retains the loop-prevention strategies of poison reverse and counting to infinity. On Cisco
routers, RIPv2 has the same administrative distance as RIPv1, which is 120. Finally, RIPv2
uses the IP address 224.0.0.9 when multicasting route updates to other RIP routers. As in
RIPv1, RIPv2 by default summarizes IP networks at network boundaries. You can disable
autosummarization if required.
Yo u c a n u s e R I P v 2 i n s m a l l n e t w o r k s w h e r e V L S M i s r e q u i r e d . I t a l s o w o r k s a t t h e e d g e o f
larger networks.
Authentication
Authentication can prevent communication with any RIP routers that are not intended to
be part of the network, such as UNIX stations running routed . Only RIP updates with the
authentication password are accepted. RFC 1723 defines simple plain-text authentication
for RIP v2.
MD5 Authentication
In addition to plain-text passwords, the Cisco implementation provides the ability to use
message digest 5 (MD5) authentication, which is defined in RFC 1321. MD5 is a hashing
algorithm that takes a variable-length string of text and produces a fixed-length 128-bit
output. One significant advantage to hashing plaintext is that the original message cannot
be reconstituted even with knowledge of the hash algorithm. This provides greater secu-
rity than using plaintext authentication.
RIPv2 Routing Database
RIPv2 maintains a routing table database as in Ve r s i o n 1. The difference is that it also keeps
the subnet mask information. The follow ing list repeats the table information of RIPv1:
IP address: The 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 must be used to reach the destination
Metric: A number indicating the number of hops to the destination
Timer: The amount of time since the route entry was last updated
 
 
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