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DES-7200 Configuration Guide Chapter 6 BGP
Configuration
6-36
is 0, namely the AS number of 65536 in asplain format will be represented as 1.0
in asdot+ format. Also, the AS number of 65534 in asplain format will be
represented as 65534 in asdot+ format (without displaying the 0 value).
6.23.1 Working principle
With the introduction of 4-octet AS number, there comes the problem of
establishing BGP connection between an old bgp speaker supporting only 2-octet
AS number and a new bgp speaker supporting 4-octet AS number. If the
autonomous system to which the new bgp speaker belongs uses 4-octet AS
number, then the old bgp speaker shall use the reserved AS number of 23456 to
replace the 4-octet AS number of new bgp speaker while creating the neighbor. In
the packets sent from new bgp speaker to old bgp speaker, 23456 will also be
used to replace the 4-octet AS number in the domain of "My Autonomous
System". Meanwhile, in the UPDAT packets sent to old bgp speaker, 23456 will
also be used to replace the 4-octet AS number existing in AS-PATH and
AGGREGATOR attributes; such packets will also carry the true 4-octet AS
number preserved in the optional transitive attributes of AS4-PATH and
AS4-AGGREGATOR, so that the true AS-PATH attribute and AGGREGATOR
attribute can be restored when this route arrives at the next new bgp speaker.
In other cases, the true AS number of peer side is directly used to create
neighbor.
6.23.2 Protocol specification
RFC 4893
RFC 5396
6.23.3 Configuring BGP instance with 4-octet AS number
By default, BGP protocol is not enabled. After enabling BGP protocol, the decimal
value is by default used to represent 4-octet AS number.
Command Function
DES-7200 # configure terminal
Enter global configuration mode
DES-7200(config)# router bgp
65538
Enable BGP protocol and configure device
AS number as 65538
DES-7200(config)# router bgp
1.2
You can also use asdot+ format 1.2 to
represent four-octet AS number of 65538
DES-7200(config-router)# end
Return to privileged mode.
DES-7200 # write
(Optional) Save configurations.