Huawei Quidway NetEngine80E Configuration Manual page 798

HUAWEI NetEngine80E/40E Router
Configuration Guide - IP Routing
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Issue 02 (2014-09-30)
3. Run:
ipv4-family unicast
The IPv4 unicast address family view is displayed.
4. Run:
peer { ipv4-address | group-name } public-as-only [ force ]
The device is configured to delete private AS numbers (if any) from the AS-Path
attribute before sending update packets.
An AS number ranges from 1 to 4294967295. A public AS number ranges from 1 to
64511, and from 65536 (1.0 in the x.y format) to 4294967295 (65535.65535 in the
x.y format). A private AS number ranges from 64512 to 65534. The AS number 65535
is reserved for particular use.
The peer public-as-only command can be used only on EBGP peers.
After the command without force is run, the device does not delete the private AS
numbers from the AS-Path attribute before sending update packets in either of the
following scenarios:
– The AS_Path of a route contains the AS number of the peer. In this case, deleting
the private AS numbers may lead to a routing loop.
– The AS_Path list contains both public network AS number and private AS number.
This list indicates that the route passes the public network. deleting the private AS
numbers may lead to forwarding error.
To enable the device to delete the private AS numbers from the AS-Path attribute
before sending update packets even in the preceding scenarios, specify force in the
command.
Set the maximum number of AS numbers in the AS_Path attribute.
1. Run:
system-view
The system view is displayed.
2. Run:
bgp { as-number-plain | as-number-dot }
The BGP view is displayed.
3. Run:
as-path-limit as-path-limit-num
The maximum number of AS numbers in the AS_Path attribute is set.
By default, a maximum of 255 AS numbers can be contained in the AS_Path attribute.
After the as-path-limit command is run on a device, the device checks whether the
number of AS numbers in the AS_Path attribute of a received route exceeds the
maximum value. If the number of AS numbers exceeds the maximum value, the route
is discarded. If the maximum number of AS numbers in the AS_Path attribute is too
small, routes whose number of AS numbers exceeding the maximum value will be
discarded.
Prevent a BGP device from checking the first AS number contained in the AS_Path attribute
of an Update message received from an EBGP peer.
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8 BGP Configuration
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