Date of Issue: 04-01-2023

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I. Foreword
II. What Is the Problem To Be Solved?

A. Playing in the Big I-Internet
B. When do you need BGP?

1. Which Number to Use?
2. Multilinking and Multihoming
3. Ingress Filtering
4. Multihoming to Multiple POPs of a Single ISP
5. Transit
6. Transit without Provider Independent Address Space

C. So what does the Protocol Do?
D. A Life Cycle

III. Routing Policies

A. So, what's a policy?
B. What does BGP Advertise?
C. Acceptance Policies
D. AS Paths
E. Transit vs. Peer
F. Closest Exit Routing
G. Asymmetrical Routing

IV. The Protocol Itself

A. BGP Stack
B. Protocol Interactions

1. OPEN Message
2. UPDATE Message
3. KEEPALIVE Message
4. NOTIFICATION Message
5. Route Refresh Message

C. Attributes

1. Categories of Attributes
2. The Attributes Themselves
3. ORIGIN (Type Code 1)
4. AS_PATH (Type Code 2)
5. NEXT_HOP (Type Code 3):
6. MULTI_EXIT_DISC (Type Code 4):
7. LOCAL_PREF (Type Code 5):
8. ATOMIC_AGGREGATE (Type Code 6) and AGGREGATOR (Type Code 7)
9. COMMUNITIES (Type Code 8)
10. ORIGINATOR_ID (Type code 9) and CLUSTER_LIST (Type code 10)

V. Basic Processing of BGP Routes

A. General Cisco Route Installation

1. RIBs and FIBs
2. Previously Unknown Route
3. More Specific Route
4. Lower Administrative Distance

B. The Basic Algorithm

VI. Practical Internet Routing

A. Autonomous Systems and Their Numbers
B. Joining the Club
C. Registering a Routing Policy

VII. BGP Configuration Overview

A. Minimal Configuration

1. Router ID and loopback interface
2. Basic Definition of Routes to be Advertised
3. Identifying Peers

B. Monitoring BGP
C. Multilinking and Multihoming
D. Basic iBGP
E. Redistribution

VIII. Conclusion and Looking Ahead
IX. References

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