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DES-7200 Configuration Guide Chapter 6 BGP
Configuration
6-67
6.30.11 Configuring Typical BGP 4-Octet AS
Networking requirements
BGP connection is established between the router supporting 2-octet AS
number and the router supporting 4-octet AS number (using 2-octet AS
number);
BGP connection is established between the router supporting 2-octet AS
number and the router supporting 4-octet AS number (using 4-octet AS
number);
BGP connection is established between routers supporting 4-octet AS
number, with one router using 2-octet AS number and the other router using
4-octet AS number.
Network topology
As shown below, Router A, Router B and Router C are edge routers of three
autonomous systems, and BGP connections have been established between
them. Router A only supports 2-octet AS number; Router B and Router C support
4-octet AS number. The autonomous system to which Router A belongs uses a
2-octet AS number of 64496; the autonomous system to which Router B belongs
uses a 2-octet AS number of 64497; the autonomous system to which Router C
belongs uses a 4-octet number of 1.2.
Fig 18 BGP 4-Octet AS configuration
Configuration tips
Router A cannot recognize the 4-octet AS number of 1.2 used by the