1. Intro to BGP All-Day Tutorial Avi Freedman [email_address]

5. Internet Connectivity Overview

7. Multihoming Without BGP

13. Multihoming Without BGP - How it Works

22. What is BGP?

25. Purpose of BGP

27. Basic BGP Concepts

29. BGP AND ASNs AS 4969 AS 5000 AS 6461 AS 701 AS 12001

33. CISCO DIAGRAM - RIB FIB ETC

34. Basic BGP Concepts - The BGP Route and Route Attributes

38. Next Hop Self AS701 AS3561 AS3847 A B C D AS1 198.32.184.19 198.32.184.116 198.32.184.42 198.32.184.56

50. iBGP vs. eBGP

52. iBGP AS 3847 When BGP speakers in the same AS form a BGP connection for the purpose of exchanging routing information, they are said to be running IBGP or internal BGP. IBGP speakers are usually fully-meshed. B A c

53. eBGP (1) AS 3561 AS 3847 When BGP speakers in different ASs form a BGP connection for the purpose of exchanging routing information, they are said to be running EBGP or external BGP. EBGP peers are usually directly connected. B A

54. eBGP (2) AS 2033 AS 4200 AS 7007 AS 2041

55. iBGP and eBGP Diagram AS 7007 XP AS 1239 AS 6079 AS 701 AS 4006

58. Logical view of 16 routers, fully meshed

63. Basic BGP Concepts Inserting Routes into BGP

68. Basic BGP Advertising Routes

73. Filtering BGP Routes - BGP Policy Control

76. Distribute List (2) router bgp 3847 neighbor 207.240.8.246 remote-as 8130 neighbor 207.240.8.246 distribute-list 127 in neighbor 207.240.8.246 distribute-list 101 out access-list 127 permit ip host 207.19.74.0 host 255.255.255.0 access-list 127 permit ip host 208.198.100.0 host 255.255.252.0 access-list 127 permit ip host 208.204.80.0 host 255.255.252.0 access-list 127 permit ip host 208.212.249.0 host 255.255.255.0 access-list 127 permit ip host 207.240.120.0 host 255.255.255.0 access-list 127 permit ip host 208.220.144.0 host 255.255.248.0 access-list 127 permit ip host 208.225.192.0 host 255.255.240.0 access-list 127 deny ip any any ! explicit deny if not specified

77. Distribute List (3) access-list 10 deny ip 10.0.0.0 0.255.255.255 access-list 10 deny ip 127.0.0.0 0.255.255.255 access-list 10 deny ip 128.0.0.0 0.0.255.255 access-list 10 deny ip 172.16.0.0 0.15.255.255 access-list 10 deny ip 191.255.0.0 0.0.255.255 access-list 10 deny ip 192.0.2.0 0.0.0.255 access-list 10 deny ip 192.168.0.0 0.0.255.255 access-list 10 deny ip 223.255.255.0 0.0.0.255 access-list 10 deny ip 224.0.0.0 31.255.255.255 access-list 10 deny ip 207.240.0.0 0.0.3.255 access-list 10 permit ip any A sanity filter like this keeps your table neat and prevents you from advertising crud to your peers.

82. Applying AS Path Filtering 3847 6201 D A C B E 701 F 6202 G The following configuration could be used on router B to accept routes from AS6201 & 6202 and deny all others. ip as-path access-list 10 permit ^6201$ ip as-path access-list 10 permit ^6201_6202$ ip as-path access-list 10 deny .*

89. Basic BGP Selecting Routes

93. Hardware for BGP

99. Multihoming with BGP An Introduction

105. Multihoming - Minimal BGP (for cheap routers)

113. Multihoming with BGP - Taking Customer Routes (an intermediate solution)

118. Multihoming with BGP - Taking Full Routes

122. Logistics of becoming Multihomed

124. Multihoming to the same Provider

126. The Network Grows - Supporting BGP Customers

130. Hot Potato vs. Hop-by-Hop Routing

135. TUNING INBOUND BGP ANNOUNCEMENTS

143. TUNING OUTBOUND BGP ANNOUNCEMENTS

149. PEERING WITH OTHER ISPS

151. PEERING AND next-hop-self

153. Next-Hop-Self Issues: Bad XP AS 701 192.41.177.241 AS 4969 192.41.177.87 AS 6666 192.41.177.4 10.10.10.0/24 6666 192.41.177.4 Prefix AS-Path Next-hop AS 6666 says to AS 4969: AS 4969 says to AS 701: Prefix AS-Path Next-hop 10.10.10.0/24 4969 6666 192.41.177.4

154. Next-Hop-Self Issues: Better XP AS 701 192.41.177.241 AS 4969 192.41.177.87 AS 6666 192.41.177.4 10.10.10.0/24 6666 192.41.177.4 Prefix AS-Path Next-hop AS 6666 says to AS 4969: AS 4969 says to AS 701: Prefix AS-Path Next-hop 10.10.10.0/24 4969 6666 192.41.177.87

155. BACKUP TRANSIT

156. STABLE BGP

160. BGP Dampening BGP dampening is used to minimize instability caused by route flapping and oscillation over the network. To accomplish this, values are defined to identify badly behaved routes. Genuity currently uses Cisco's default values which basically say 'flap 3 times in 15 minutes and your damped': half-life 15 minutes penalty 1000 suppress-value 2000 reuse-value 750 But in time it can become a bit more complex. Each time a route flaps it gets a penalty (1000). If the cumulative penalty is greater than the suppress-value (2000, so 3 flaps), the advertisement of the route will be suppressed. The penalty will be exponentially decayed based on the half-life . Once the penalty decreases below the predefined reuse-value , the advertisement will be unsuppressed. The default maximum suppress time is 4 times the half-life . This ensures that if a route flaps a lot in a very short period but quickly becomes stable it's only suppressed for a maximum of 1 hour. Route flap dampening is not applied to routes originated from the AS in which the router resides.

161. eBGP Multihop

164. SUPPORTING MULTI-HOMED CUSTOMERS

167. IGP REDISTRIBUTION

168. SCALING WITH CONFEDERATIONS

170. Logical View of full 16-router Mesh (kudos to danny@genuity)

171. Confederations C C C C C C C C C C C C C AS 1239 AS 701 AS 4969 AS 64512 AS 64513 AS 64514

173. SCALING WITH ROUTE REFLECTORS

175. Other Issues

177. CISCO CONFIGURATION