BGP

BGP Fundamentals

BGP Best Path Selection

BGP installs the first received path as the best path automatically. When additional paths are received for the same network ...
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/ BGP, BGP Best Path Selection, BGP Intro

BGP Packets

BGP uses a variety of messages for establishing the connection, exchanging routing information, checking if the remote BGP neighbor is ...
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/ BGP, BGP Intro, BGP Packets

BGP Neighbor States

BGP requires a neighbor relationship to be established before any information is exchanged between BGP speakers. Like most other dynamic ...
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/ BGP, BGP Intro, BGP State Machine

BGP Fundamentals

BGP A router’s primary function is to move packets from one network to a different network. A router learns about ...
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/ BGP, BGP Intro

Tshoot Route Advertisement

Complete Route Advertisement Process

Complete Route Advertisement The complete BGP route advertisement process must take into account routes that are advertised locally and routes ...
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/ BGP, Route Adv

Local Route Advertisement

A BGP router can advertise or receive updates from its BGP peer only if it has achieved the Established state ...
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/ BGP, Route Adv

The BGP Tables

BGP uses three tables for maintaining a network prefix and the path attributes (PA) associated with each path for a ...
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/ BGP, Route Adv

Tshoot Missing BGP Routes

Reasons that route advertisement fails between BGP peers are as follows: Next-Hop Check Failure Bad Network Design Validity Check Failure ...
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/ BGP, Route Adv

BGP Advanced

Conditional Matching

Filtering of Prefixes by Route Policy The last component for finding missing BGP routes is through the examination of the ...
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/ Advanced BGP, BGP, RouteFiltering

BGP Communities

BGP Communities BGP communities are an optional transitive BGP attribute that can traverse from autonomous system to autonomous system. A ...
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/ Advanced BGP, BGP, RouteFiltering

BGP Multihoming and Multipath

BGP Multipath Unlike most routing protocols, BGP only selects a single best path for each prefix. It doesn’t do ECMP ...
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/ Advanced BGP, BGP, LoadSharing

Policy Control

Policy Control Using BGP Attributes Most commonly used BGP attributes: LOCAL_PREF AS_PATH MED ORIGIN NEXT_HOP WEIGHT BGP picks a best ...
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BGP HA

BGP fast-external-fallover

BGP Fast-external-fallover command terminates external BGP sessions of any directly adjacent peer if the link used to reach the peer ...
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/ BGP, BGP HA

BGP Nonstop Routing (NSR)

High-availability features like GR are really useful in critical network environments, where traffic loss even for few seconds can cost ...
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/ BGP, BGP HA, NSR

BGP Graceful-Restart Feature (GR)

NSF/SSO, NSR, Graceful Restart Nonstop forwarding (NSF) refers to the capability of the data plane to continue forwarding IP packets ...
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/ BGP, BGP HA, Graceful-Restart, NSF, SSO

BGP Graceful Restart (GR)

NSF/SSO, NSR, Graceful Restart Nonstop forwarding (NSF) refers to the capability of the data plane to continue forwarding IP packets ...
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/ BGP, BGP HA, Graceful-Restart, NSF, SSO

BGP Convergence

Understanding BGP Route Convergence

BGP Route Convergence What is Routing Convergence? Routing convergence can be broadly defined as how quickly a routing protocol can ...
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BGP Configs

IBGP Next-Hop Behavior

The EBGP next-hop attribute is the IP address that is used to reach the advertising router. For EBGP peers, the ...
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/ BGP, BGP CMD

EBGP Multihop

By default, EBGP neighbors exchange packets with a TTL (Time To Live) set to 1. If you attempt to establish ...
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/ BGP, BGP CMD

4-Byte AS Numbers

Table of Contents Prior to January 2009, BGP autonomous system (AS) numbers that were allocated to companies were two-octet numbers ...
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/ BGP, BGP CMD

Scaling BGP

Maximum Prefixes

Maximum Prefixes The BGP Maximum-Prefix feature allows you to control how many prefixes can be received from a neighbor. By ...
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/ BGP, Scaling BGP

Outbound Route Filtering (ORF)

ORF ORF allows you to build a prefix-list on a router, then send it to a BGP peer. The BGP ...
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/ BGP, ORF, Scaling BGP

Tuning BGP CPU

BGP is a heavy protocol and can consume a lot of CPU cycles. Use the following features to improve the ...
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Tuning BGP Memory

Scaling BGP Functions BGP is a heavy protocol because it uses the most CPU and memory resources on a router ...
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/ BGP, Scaling BGP