Border Gateway Protocol IPv4 (BGPv4)
This chapter provides a general description of BGPv4 as it is supported in the Dell Networking Operating System (OS).
BGP protocol standards are listed in the
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 first (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.
Topics:
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Implement BGP with Dell Networking OS
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BGP Regular Expression Optimization
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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 identifies 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), defined by their connections and operation.
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multihomed AS
— is one that maintains connections to more than one other AS. This group allows the AS to remain connected to the
Internet in the event of a complete failure of one of their connections. However, this type of AS does not allow traffic from one AS to
pass through on its way to another AS. A simple example of this group is seen in the following illustration.
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stub AS
— is one that is connected to only one other AS.
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transit AS
— is one that provides connections through itself to separate networks. For example, in the following illustration, Router 1
can use Router 2 (the transit AS) to connect to Router 4. Internet service providers (ISPs) are always transit ASs, because they provide
connections from one network to another. The ISP is considered to be “selling transit service” to the customer network, so thus the
term Transit AS.
When BGP operates inside an AS (AS1 or AS2, as seen in the following illustration), it is referred to as Internal BGP (IBGP Internal Border
Gateway Protocol). When BGP operates between ASs (AS1 and AS2), it is called External BGP (EBGP External Border Gateway Protocol).
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Border Gateway Protocol IPv4 (BGPv4)
Summary of Contents for S4048T-ON
Page 1: ...Dell Configuration Guide for the S4048 ON System 9 11 2 1 ...
Page 148: ...Figure 10 BFD Three Way Handshake State Changes 148 Bidirectional Forwarding Detection BFD ...
Page 251: ...Dell Control Plane Policing CoPP 251 ...
Page 363: ... RPM Synchronization GARP VLAN Registration Protocol GVRP 363 ...
Page 511: ...Figure 64 Inspecting the LAG Configuration Link Aggregation Control Protocol LACP 511 ...
Page 558: ...Figure 84 Configuring Interfaces for MSDP 558 Multicast Source Discovery Protocol MSDP ...
Page 559: ...Figure 85 Configuring OSPF and BGP for MSDP Multicast Source Discovery Protocol MSDP 559 ...
Page 564: ...Figure 88 MSDP Default Peer Scenario 2 564 Multicast Source Discovery Protocol MSDP ...
Page 565: ...Figure 89 MSDP Default Peer Scenario 3 Multicast Source Discovery Protocol MSDP 565 ...
Page 841: ...Figure 115 Single and Double Tag TPID Match Service Provider Bridging 841 ...
Page 842: ...Figure 116 Single and Double Tag First byte TPID Match 842 Service Provider Bridging ...