Information Technology Reference
In-Depth Information
Figure 4-13 shows the final topology.
Figure 4-13
Final Topology
AS 400
R7
172.16.0.0/16
172.16.0.0/16
AS 300
AS 200
R4
R5
R6
Local-as 100
172.15.0.0/16
AS 2
172.15.0.0/16
172.15.0.0/16
R1
R2
R3
Summary
This chapter presented various techniques you can use to create complex and effective BGP
policies. The chapter started with one of the fundamental techniques, regular expressions.
Regular expressions are used extensively in IOS for pattern matching in parsing command
outputs and in defining AS_PATH and community patterns.
A variety of filtering tools also were discussed. They include prefix lists, community lists,
AS_PATH lists, route maps, and policy lists, all of which are used extensively in creating
BGP policies. Additionally, more-complex policy tools were presented, including condi-
tional advertisement, aggregation, deaggregation, Local AS, QoS policy propagation, and
policy accounting. The chapter ended with a case study on AS merging using the Local AS
feature.
