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DES-7200 Configuration Guide Chapter 6 BGP
Configuration
6-35
one peer, which equals to virtualizing an AS . when the real AS changes, you still
can establish BGP connection without modifying the BGP cofniguration of the
peer. Local AS applies to AS migration and converge of large networks without
influencing the configurations of the devices in other interconencted ASs.
When establishing the BGP connection, the local device will advertise local AS
number to the peer in the OPEN message. The peer checks whether the AS
number matches the locally configured one and refuses the BGP connection if
there is a difference. By default, the local AS of the BGP connection is the real
BGP AS. With this function, the local device replaces the real AS with the
configured one to establish the BGP connection.
To configure local AS for one peer, execute the following commands:
Command Function
DES-7200 # configure terminal Enter the global configuration mode.
DES-7200(config)# router bgp 500
Enter the BGP configuration mode.
DES-7200(config-router)# neighbor
192.168.195.64 remote-as 100
Configure the peer.
DES-7200(config-router)# neighbor
192.168.195.64 local-as 300
Configure AS 300 as the local AS for
the peer
The local AS function applies to only EBGP peers, not IBGP peers, confederation
EBGP peers. Meanwhile, there are some limits as below:
The local AS cannot be configured as the remote as of the peer.
Local AS cannot be configured for one member of the peer group.
The local AS cannot be configured as the real BGP AS.
The local AS cannot be configured as the AS number of the confederation if
the device is the member of one confederation.
For details of the neighbor peer-address local-as as-num command, refer to
Command Reference.
6.23 BGP 4-Octet AS Configuration
The traditional AS number consists of two octets within the range of 1-65535. The
AS number defined by RFC4893 consists of 4 octets falling within the range of
1-4294967295, so as to address the problem of limited AS number resource.
According RFC5396, 4-octet AS number supports two representation formats:
asplain and asdot+. The asplain (decimal) representation is the same as the
former representation format, namely the 4-octet AS number will be represented
using decimal value. The asdot+ representation is featured by ([high order 2
octets.] low order 2 octets). The high order 2 octets won't be displayed if the value