Table of Contents
Border Gateway Protocol – BGP4
Border Gateway Protocol (BGP4)
BGP Part 0
Consider a typical small ISP in Africa
Small ISP with one upstream provider
What happens with other ISPs in the same country
Why use BGP? Keeping Local Traffic Local
Why use BGP? Keeping Local Traffic Local
Consider a larger ISP with multiple upstreams
A Large ISP with more than one upstream provider
Terminology: “Policy”
Terminology: “Peering” and “Transit”
Terminology: “Aggregation”
Policy Issues
Summary: Why do I need BGP?
BGP Part 1
Routing versus Forwarding
Routing Table/RIB
Forwarding Table/FIB
Routing Tables Feed the Forwarding Table
IP Routing
IP Routing
IP routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
IP route lookup: Longest match routing
Static vs. Dynamic routing
Dynamic Routing
BGP Part 2
Interior vs. Exterior Routing Protocols
IGP
EGP
Why Do We Need an EGP?
Scalability and policy issues
Scalability: Not using static routes
Scalability: Not using IGP (OSPF)
Using BGP instead
BGP Part 3
BGP Building Blocks
Autonomous System (AS)
Autonomous System (AS)
Autonomous System (AS)
Autonomous System numbers
Using AS numbers
Routing flow and packet flow
Egress Traffic
Ingress Traffic
Types of Routes
Hierarchy of Routing Protocols
DeMarcation Zone (DMZ)
Basics of a BGP route
BGP Part 4
Basic BGP commands
Inserting prefixes into BGP
“network” command
“redistribute static”
“redistribute static”
Aggregates and Null0
BGP Case Study 1 and Exercise 1
Case Study 1: Small ISP with one upstream provider
Case Study 1: Small ISP with one upstream provider
Case Study 1: Routing Protocols
Case Study 1: BGP is not needed
Exercise 1: Upstream provider with small customers
Exercise 1: Upstream provider with small customers
Exercise 1: BGP configuration
Exercise 1: Transit through upstream provider
Exercise 1: What you should see
Exercise 1: Did BGP “network” statement work?
BGP Part 5
BGP Protocol Basics
BGP Protocol Basics
Terminology
Terminology
BGP Basics …
Interior BGP vs. Exterior BGP
BGP Peers
BGP Peers – External (eBGP)
BGP Peers – Internal (iBGP)
Configuring eBGP peers
Configuring iBGP peers
Configuring iBGP peers: Full mesh
Configuring iBGP peers: Loopback interface
Configuring iBGP peers
Configuring iBGP peers
Configuring iBGP peers
BGP Part 6
BGP Updates — NLRI
BGP Updates — Attributes
AS-Path Attribute
Next Hop Attribute
Next Hop Attribute
Next Hop Attribute
Next Hop Attribute (more)
Community Attribute
BGP Updates – Withdrawn Routes
BGP Updates – Withdrawn Routes
BGP Routing Information Base
BGP Routing Information Base
BGP Routing Information Base
BGP Routing Information Base
BGP Routing Information Base
BGP Routing Information Base
An Example…
BGP Case Study 2 and Exercise 2
Case Study 2: Another ISP in the same country
Case Study 2: Another ISP in the same country
Case Study 2: Bringing down costs
Case Study 2: Keeping Local Traffic Local
Exercise 2: Connect to another local ISP
Exercise 2: BGP configuration
Exercise 2: What you should see
Exercise 2: What you should see
Exercise 2: Do you see transit routes through your peers?
BGP Part 7
Terminology: “Policy”
Routing Policy
Filter list rules: Regular Expressions
Regular expressions (cisco specific)
Filter list – using as-path access list
Policy Control – Prefix Lists
Prefix Lists – Examples
Prefix Lists – More Examples
Policy Control Using Prefix Lists
Policy Control – Route Maps
Route-map match & set clauses
Route Map: Example One
Route Map: Example Two
BGP Exercise 3
Exercise 3: Filtering peer routes using AS-path
Exercise 3: Filtering peer routes using AS-path
Exercise 3: What you should see
Exercise 3: Did it work?
BGP Exercise 4
Exercise 4: Filtering peer routes using prefix-lists
Exercise 4: Filtering peer routes using prefix-list
Exercise 4: What you should see
Exercise 4: Did it work?
BGP Part 8
BGP Path Attributes: Why ?
BGP Path Attributes...
AS-PATH
AS-Path
Next-Hop
Third Party Next Hop
Next Hop...
Local Preference
Local Preference
Multi-Exit Discriminator
Multi-Exit Discriminator (MED)
Origin
Communities
Communities
Weight
Administrative Distance
Synchronization
Synchronization
BGP route selection (bestpath)
BGP route selection (bestpath)
BGP route selection (bestpath)
BGP Route Selection...
BGP Exercise 5
Exercise 5: Configure iBGP
Exercise 5: Configure iBGP
Exercise 5: Configure iBGP
Exercise 5: What you should see
BGP Part 9
PPT Slide
Stub AS
PPT Slide
Multi-homed AS
Service Provider Network
Common Service Provider Network
Load-sharing – single path
Load-sharing – multiple paths from the same AS
Redundancy – Multi-homing
Default from all providers
Default from all providers
Customer prefixes plus default from all providers
Customer routes from all providers
Full routes from all providers
Full routes from all providers
Best Practices IGP in Backbone
Best Practices... Connecting to a customer
Best Practices... Connecting to other ISPs
Best Practices... The Internet Exchange
Summary
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