Chapter 6. RIPv2, RIPng, and Classless Routing

This chapter covers the following subjects:

• Operation of RIPv2

• Operation of RIPng

• Configuring RIPv2

• Configuring RIPng

• Troubleshooting RIPv2 and RIPng

RIP Version 2 (RIPv2) is defined in RFC 1723^[1] and is supported in IOS Versions 11.1 and later. RIPv2 is not a new protocol; rather, it is RIPv1 with some extensions to bring it more up to date with modern routing environments. These extensions are

^[1] Supplemental to this RFC are RFC 1721, "RIP Version 2 Protocol Analysis," and RFC 1722, "RIP Version 2 Protocol Applicability Statement."

• Subnet masks carried with each route entry

• Authentication of routing updates

• Next-hop addresses carried with each route entry

• External route tags

• Multicast route updates

The most important of these extensions is the addition of a Subnet Mask field to the routing update entries, enabling the use of variable-length subnet masks and qualifying RIPv2 as a classless routing protocol.

RIPv2 is the first of the classless routing protocols discussed in this book. As such, this chapter serves as an introduction to classless routing, and to RIPv2.

RIP next generation (RIPng), a modification of RIPv2 for routing IPv6, is also covered in this chapter. Unlike IPv4, IPv6 is inherently classless; there are no class A, B, and C, or similar address groupings. Therefore RIPng is also a classless routing protocol.