network 9.1.2.0 0.0.0.255
#
return
8.28.3 Example for Configuring AS_Path Filters
AS_Path filters can be used as needed to improve network performance.
Networking Requirements
Enterprises A, B, and C belong to different ASs. Enterprise B's network communicate with the
networks of the other two enterprises through EBGP. Due to the competition relationship,
enterprises A and C hope that the routes that they advertise to enterprise B are not learned by
each other. An AS_Path filter is configured on enterprise B's network to address this problem.
On the network shown in
, Router B establish EBGP connections with Routers A
and C. To disable devices in AS 10 from communicating with devices in AS 30, you can
configure an AS_Path filter on Router B to prevent devices in AS 20 from advertising routes of
AS 30 to AS 10 or routes of AS 10 to AS 30 in order to isolate AS 10 and AS 30.
Figure 8-31
Networking diagram for configuring AS_Path filters
GE1/0/0
9.1.1.1/24
POS2/0/0
200.1.2.1/24
RouterA
AS 10
POS2/0/0
200.1.2.2/24
RouterB
AS 20
POS2/0/0
200.1.3.2/24
RouterC
AS 30
POS3/0/0
200.1.3.1/24
EBGP
EBGP
GE1/0/0
20.1.1.1/24
Configuration Roadmap
The configuration roadmap is as follows:
1.
Establish EBGP connections between Routers A and B and between Routers B and C and
configure these devices to import direct routes so that the ASs can communicate with each
other through these EBGP connections.
2.
Configure AS_Path filters on Router B and use filtering rules to prevent AS 20 from
advertising routes of AS 30 to AS 10 or routes of AS 10 to AS 30.
Data Preparation
To complete the configuration, you need the following data:
HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
8 BGP Configuration
Issue 02 (2014-09-30)
Huawei Proprietary and Confidential
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