IPv6 Essentials, 2nd Edition

Chapter 8. Routing Protocols

Forwarding an IPv6 datagram beyond a directly attached subnet requires a router. Routers look at the datagram’s destination IPv6 address and search for a matching prefix in their local routing tables. The first section of this chapter explains the routing table. It is very important for the router to have all relevant destinations in its routing table. But how do they get there? Entering them manually on all routers would not be very economical. A much more efficient automatic approach can be achieved by deploying routing protocols. Routing protocols define exchange procedures to synchronize the routing table between routers dynamically. Routing information needs to be distributed either within an autonomous system (AS) or between autonomous systems. An AS is defined as a set of networks governed by a single authority. Routing protocols that distribute information within an AS are called Interior Gateway Protocols (IGP). OSPF for IPv6, RIPng, IPv6 support on integrated IS-IS, and EIGRP for IPv6 belong to this category. Protocols that distribute information between ASes are called Exterior Gateway Protocols (EGP). BGP-4 and its extensions for IPv6 represent such a protocol.

This chapter explains the routing protocols RIPng, OSPF for IPv6, and BGP-4 support for IPv6 in detail. They represent the most important routing protocols in use today. The last section, "Additional Routing Protocols for IPv6,” gives a brief description of IS-IS for IPv6 and EIGRP ...