160 | Border Gateway Protocolw w w . d e l l . c o m | s u p p o r t . d e l l . c o m • Multiprotocol BGP• Implementing BGP with FTOS• Additional Path (Add-Path) support• Advertise IGP cost as MED for redistributed routes• Ignore Router-ID for some best-path calculations• 4-Byte AS Numbers• AS4 Number Representation• AS Number Migration• BGP4 Management Information Base (MIB)• Important Points to Remember• Configuration Information• Configuration Task List for BGP• MBGP Configuration• Storing Last and Bad PDUs• Capturing PDUs• PDU Counters• Sample ConfigurationsBGP protocol standards are listed in the Appendix 50, Standards Compliance chapter.Protocol OverviewBorder Gateway Protocol (BGP) is an external gateway protocol that transmits interdomain routinginformation within and between Autonomous Systems (AS). Its primary function is to exchange networkreachability information with other BGP systems. BGP generally operates with an Internal GatewayProtocol (IGP) such as OSPF or RIP, allowing you to communicate to external ASs smoothly. BGP addsreliability to network connections having multiple paths from one router to another.Autonomous Systems (AS)BGP Autonomous Systems (ASs) are a collection of nodes under common administration, with commonnetwork routing policies. Each AS has a number, already assigned by an internet authority. You do notassign the BGP number.AS Numbers (ASNs) are important because the ASN uniquely identifies each network on the Internet. TheIANA has reserved AS numbers 64512 through 65534 to be used for private purposes. The ASNs 0 and65535 are reserved by the IANA and should not be used in a live environment.Autonomous Systems can be grouped into three categories, defined by their connections and operation.
