The "Foundation Summary" is a collection of quick reference information that provides a convenient review of many key concepts in this chapter. For those of you who already feel comfortable with the topics in this chapter, this summary will help you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your final preparations before the exam, these tables and figures will be a convenient way to review the day before the exam.
• BGP-4 is an enhanced distance vector protocol.
• BGP-4 creates and maintains connections between peers, using TCP port 179.
• The connection is maintained by periodic keepalives.
• The failure to see a keepalive, an update, or a notification is the means by which destination networks and paths to those destinations are tracked. Any change in the network results in a triggered update.
• The metric used in BGP-4 is intricate and is the source of its complexity and its strength. The metric, referred to as attributes, allows great granularity in path selection.
• The use of hierarchical addressing and the capability to manipulate traffic flow results in a network that is designed to grow.
• BGP-4 has its own routing table, although it is capable of both sharing and inquiring of the interior IP routing table.
• It is possible to manipulate the traffic flow by using the complex metric called attributes, but policy-based routing is based on the hop-by-hop paradigm. This means that no router can send traffic on a route that the next-hop router would not choose for itself.
Tables 8-5 through 8-7 summarize the information that you will need to be familiar with to master the objectives of this chapter.
Table 8-5 The Four Categories of Attributes
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