Huawei Quidway NetEngine80E Configuration Manual page 953

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
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Table 8-24
Table 8-24 AS_Path-based route selection rules
Item
AS_Set
AS_Confed_Sequence and
AS_Confed_Set
bestroute as-path-ignore
apply as-path
peer public-as-only
Issue 02 (2014-09-30)
AS_Confed_Set: records in random order all the sub-ASs within a BGP confederation
through which a route passes from the local device to the destination.
describes the AS_Path-based route selection rules.
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Description
BGP takes an AS_Set as one AS number even if the AS_Set
contains multiple AS numbers.
When the aggregate (BGP) command is configured to
generate a manually summarized route, if as-set is specified
in the command, AS_Set will be carried in the summarized
route. The information in the AS_Set is as follows:
l If the routes used in the summarization carry the same
AS_Sequence, this AS_Sequence is carried in the
summarized route, and the AS_Set of the summarized
route is null.
l If the routes used in the summarization carry different
AS_Sequences, all the AS numbers carried in the
AS_Sequences are included in the AS_Set of the
summarized route.
BGP ignores AS_Confed_Sequence and AS_Confed_Set
when calculating the AS_Path length.
After the command is configured, BGP does not compare
the AS_Path attribute during route selection.
The command can be run to configure an apply clause for a
route-policy so that the ASs in the AS_Path of the route that
matches the route-policy are cleared or replaced, or new ASs
are added.
NOTE
The configuration of the apply as-path command may change the
traffic forwarding path, or cause routing loops or route selection
errors. Therefore, exercise caution when configuring the command.
After the command is configured, BGP deletes private AS
numbers (if any) from the AS_Path attribute before sending
Update packets. Private AS numbers range from 64512 to
65534.
8 BGP Configuration
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