Information Technology Reference
In-Depth Information
Table 7-39 spells out the comparative values of each method; its recommendations can be
boiled down into the following two general guidelines:
•
If you need to scale your IGP, you should use confederation.
•
If you do not need to scale your IGP, select the route reflection method whenever you
can to simplify migration and management.
Summary
This chapter provided a detailed discussion of two approaches to increasing iBGP scalabil-
ity. The first approach, route reflection, gets around the full iBGP mesh requirement by
relaxing the requirement for a group of routers called route reflectors (RRs). These routers
can reflect routes between the clients they serve and other iBGP peers, or nonclients.
Because clients need to peer only with RRs that serve them, the number of iBGP sessions
is reduced.
The second approach for increasing iBGP scalability is confederation, which differs from
route reflection in that it divides a large AS into a number of smaller autonomous systems,
called member autonomous systems or subautonomous systems. Because eBGP is used
between member autonomous systems, no full mesh is required.
The focus of the chapter was the design examples. For each example, proper design guide-
lines were presented, as well as the consequences of disregarding the guidelines. In addi-
tion, possible solutions were presented for each example. Chapter 8 contains four case
studies on designing and implementing migration strategies involving route reflection and
confederation.
