Huawei Quidway NetEngine80E Configuration Manual page 803

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
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Issue 02 (2014-09-30)
NOTE
If more than one IP prefix entry is defined, at least one entry should be set in permit mode.
Configure an AS_Path filter.
An AS_Path filter is used to filter BGP routes based on the AS_Path attributes contained
in the BGP routes. If you do not want traffic to pass through an AS, configure an AS_Path
filter to filter out the traffic carrying the number of the AS. If the BGP routing table of each
device on a network is large, configuring an ACL or an IP prefix list to filter BGP routes
may be complicated and make it difficult to maintain new routes.
NOTE
If the AS_Path information of a summarized route is lost, the AS_Path filter cannot be used to filter
the summarized route, but can still be used to filter the specific routes from which the summarized
route is derived.
An AS_Path filter can be used as a matching condition of a route-policy or be used in the
peer as-path-filter command.
1. Run:
system-view
The system view is displayed.
2. Run:
ip as-path-filter { as-path-filter-number | as-path-filter-name }
{ permit | deny } regular-expression
An AS_Path filter is configured.
NOTE
For details on how to use AS_Path filters, see
Expressions.
Configure a community filter.
A BGP community attribute is used to identify a group of routes with the same properties.
Routes can be classified by community attribute. This facilitates route management.
Some AS internal routes may not need to be advertised to any other AS, whereas AS external
routes need to be advertised to other ASs. These AS external routes have different prefixes
(as a result, an IP prefix list is inapplicable) and may come from different ASs (as a result,
an AS_Path filter is inapplicable). You can set a community attribute value for these AS
internal routes and another community attribute value for these AS external routes on an
ASBR to control and filter these routes.
1. Run:
system-view
The system view is displayed.
2. Run:
ip community-filter
A community filter is configured.
– To configure a standard community filter, run the ip community-filter { basic
comm-filter-name { permit | deny } [ community-number | aa:nn ]
basic-comm-filter-num { permit | deny } [ community-number | aa:nn ]
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8 BGP Configuration
8.25 Applying BGP AS_Path Regular
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