RIP Version 2 (RIPv2) is defined in RFC 1723. It is the first classless routing protocol discussed in this course. The figure places RIPv2 in its proper perspective with other routing protocols. Although RIPv2 is a suitable routing protocol for some environments, it has lost popularity when compared to other routing protocols such as EIGRP, OSPF, and IS-IS, which offer more features and are more scalable.

While it may be less popular than other routing protocols, both versions of RIP are still appropriate in some situations. Although RIP lacks the capabilities of many of the later protocols, its sheer simplicity and widespread use in multiple operating systems makes it an ideal candidate for smaller, homogeneous networks where multi-vendor support is necessary - especially within UNIX environments.

Because you will need to understand RIPv2 - even if you do not use it - this chapter will focus on the differences between a classful routing protocol (RIPv1) and a classless routing protocol (RIPv2) rather than on the details of RIPv2. The main limitation of RIPv1 is that it is a classful routing protocol. As you know, classful routing protocols do not include the subnet mask with the network address in routing updates, which can cause problems with discontiguous subnets or networks that use Variable-Length Subnet Masking (VLSM). Because RIPv2 is a classless routing protocol, subnet masks are included in the routing updates, making RIPv2 more compatible with modern routing environments.

RIPv2 is actually an enhancement of RIPv1's features and extensions rather than an entirely new protocol. Some of these enhanced features include:
Next-hop addresses included in the routing updates
Use of multicast addresses in sending updates
Authentication option available
Like RIPv1, RIPv2 is a distance vector routing protocol. Both versions of RIP share the following features and limitations:
Use of holddown and other timers to help prevent routing loops.
Use of split horizon or split horizon with poison reverse to also help prevent routing loops.
Use of triggered updates when there is a change in the topology for faster convergence.
Maximum hop count limit of 15 hops, with the hop count of 16 signifying an unreachable network.


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