Concept Guide

Border Gateway Protocol (BGP)
Border Gateway Protocol (BGP) is an interdomain routing protocol that manages routing between edge routers.
BGP uses an algorithm to exchange routing information between switches enabled with BGP. BGP determines a path to reach a particular
destination using certain attributes while avoiding routing loops. BGP selects a single path as the best path to a destination network or
host. You can also inuence BGP to select dierent path by altering some of the BGP attributes.
Topics:
• Border Gateway Protocol version 4 (BGPv4)
• Autonomous Systems (AS)
• Multiprotocol BGP
• Sessions and Peers
• Implementing BGP global and address family
• BGP Attributes for selecting Best Path
• Implement BGP with Dell EMC Networking OS
• Conguration Information
• Conguring a basic BGP network
• Enabling MBGP Congurations
• MBGP support for IPv6
• Conguring IPv6 MBGP between peers
• Example-Conguring IPv4 and IPv6 neighbors
• Congure IPv6 NH Automatically for IPv6 Prex Advertised over IPv4 Neighbor
• BGP Regular Expression Optimization
• Debugging BGP
Border Gateway Protocol version 4 (BGPv4)
This section provides a general description of BGPv4 as it is supported in the Dell EMC Networking Operating System (OS).
BGP protocol standards are listed in the Standards Compliance chapter.
BGP is an external gateway protocol that transmits interdomain routing information within and between autonomous systems (AS). The
primary function of the BGP is to exchange network reachability information with other BGP systems. BGP generally operates with an
internal gateway protocol (IGP) such as open shortest path rst (OSPF) or router information protocol (RIP), allowing you to communicate
to external ASs smoothly. BGP adds reliability to network connections by having multiple paths from one router to another.
Autonomous Systems (AS)
BGP autonomous systems (ASs) are a collection of nodes under common administration with common network routing policies.
Each AS has a number, which an internet authority already assigns. You do not assign the BGP number.
AS numbers (ASNs) are important because the ASN uniquely identies each network on the internet. The Internet Assigned Numbers
Authority (IANA) has reserved AS numbers 64512 through 65534 to be used for private purposes. IANA reserves ASNs 0 and 65535 and
must not be used in a live environment.
You can group autonomous systems into three categories (multihomed, stub, and transit), dened by their connections and operation.
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