VXLAN Fabric with BGP EVPN Control-Plane: Design Considerations - Book Description and ToC

About this book

 

The intent of this book is to explain various design models for Overlay Network and Underlay Network used in VXLAN Fabric with BGP EVPN Control-Plane. The first two chapters are focusing on the Underlay Network solution. The OSPF is introduced first. Among other things, the book explains how OSPF flooding can be minimized with area design. After OSPF there is a chapter about BGP in the Underlay network. Both OSPF and BGP are covered deeply and things like convergence are discussed. After the Underlay Network part, the book focuses on BGP design. It explains the following models: (a) BGP Multi-AS with OSPF Underlay, this chapter discusses two design models – Shared Spine ASN and Unique Spien ASN, (b) BGP-Only Multi-ASN where both direct and loopback overlay BGP peering models are explained, (c) Single-ASN with OSPF Underlay, (d) Hybrid-ASN with OSPF Underlay – Pod-specific shared ASN connected via Super-Spine layer using eBGP peering, (e) Dual-ASN model where leafs share the same ASN, and spines share their ASN. Each of the design model chapters includes a “Complexity Map” that should help readers to understand the complexity of each solution. This book also explains BGP ECMP and related to ECMP, the book also covers ESI Multihoming. The last chapter introduces how two Pods, can also be geographically dispersed DCs, can be connected using Layer 3 only DCI with MPLS.

 

I am using 5-stage Clos topology throughout the book. Some solutions are though explained by using only three switches for the sake of simplicity. I am also using IP-Only Underlay Network with Ingress-Replication, so this book does not cover Underlay Network Multicast solution. Besides, I am not covering DCI using Layer 2 Border Gateway (BGW) or Overlay Tenant Routing Multicast solution in this book because those, among the Underlay Multicast solutions, are covered in my first book “Virtual Extensible LAN – VXLAN: A Practical Guide to VXLAN solution” that is available at Amazon and Leanpub.

 

I wanted to keep the focus of the book fairly narrow and concentrate on the Control-Plane design and functionality. Please be aware that this book does not give any recommendation to which solution is the best and which is not. It is the readers' responsibility to find that out and selects the best solution for their needs. The book includes 66 full-color images, 260 configuration/show command examples, and 32 packet captures.

Table of Contents viii

Chapter 1:  Underlay Network with OSPF 1

Introduction 1

Infrastructure AS Numbering and IP Addressing Scheme 1

OSPF Neighbor Process 2

OSPF Neighbor Process: Init 3

OSPF Neighbor Process: ExStart 7

OSPF Neighbor Process: Exchange and Full 9

Shortest-Path First (SPF)/Dijkstra Algorithm 18

SPF Run – Phase I: Building a Shortest-Path Tree 19

First iteration round 20

Second iteration round 21

Third iteration round 24

SPF Run – Phase II: Adding Leafs to Shortest-Path Tree 25

Convergence 26

Flood reduction with multiple OSPF Areas 30

OSPF summarization in ABR 40

Removing OSPF Router from the Datapath 43

LSA and SPF timers 47

LSA Throttling Timer 47

Flood Pacing Timer 49

LSA Group Pacing Timer 50

Summary 51

References 52

Chapter 2:  Underlay Network with BGP 53

Introduction 53

Infrastructure AS Numbering and IP Addressing Scheme 54

BGP Configuration 55

Leaf Switches 55

Spine Switches 56

Super-Spine Switches 56

BGP Neighbor Process 57

Idle 57

Connect 57

Active 57

Finalizing negotiation of the TCP connection 58

OpenSent and OpenConfirm 61

Established 61

BGP NLRI Update Process 65

RIB to Adj-RIB-Out (Pre-Policy) 65

Adj-RIB-Out (Pre) to Adj-RIB-Out (Post) 65

Adj-RIB-In (Post) to Adj-RIB-In (Pre) 66

Adj-RIB-In (Pre) to Loc-RIB 66

Loc-RIB to RIB 66

BGP Update: Unreachable Destination 70

MRAI Timer 71

BGP AS-Path Prepend 71

OSPF and BGP Comparison 75

References 78

Chapter 3:  BGP Multi-AS with OSPF Underlay 79

Introduction 79

Inter-Switch Link IP addressing 80

Underlay Network Routing with OSPF 81

Overlay Network BGP L2VPN EVPN Peering 83

Adding L2VN segment 86

Routing comparison: Spine Sharing ASN vs. Unique ASN 88

Spine Switches Sharing ASN 88

All Switches in Unique ASN 94

BGP convergence: Group of Spines in the same AS 101

BGP convergence: All switches in unique AS 106

Complexity Chart of Multi-ASN Design with OSPF Underlay 113

Spines in shared ASN – OSPF Underlay 113

All switches in unique ASN - OSPF Underlay 114

References 115

Chapter 4:  BGP Only Multi-ASN Design 117

Introduction 117

Underlay: Direct Peering – Overlay: Loopback 117

Underlay: Direct Peering – Overlay: Direct Peering 125

Complexity Chart Multi-ASN Design with eBGP Underlay 132

Direct Underlay Peering – Loopback Overlay Peering 132

Direct Underlay Peering – Direct Overlay Peering 133

Chapter 5:  Single AS Model with OSPF Underlay 135

Introduction 135

Configuration 136

BGP Policy and BGP Update Configuration 136

Leaf Switches 136

Spine Switches 137

Super-Spine Switches 138

Verification 140

BGP L2VPN EVPN Peering 140

BGP Table Verification 140

Inconsistency Problem with Received Route Count 142

Fixing the Problem 148

Re-checking of BGP Tables 151

NVE Peering 154

MAC Address Table and L2RIB 156

Data-Plane Testing 158

Complexity Chart 159

Single-AS Design with OSPF Underlay 159

Chapter 6:  Hybrid AS Model with OSPF Underlay 161

Introduction 161

Configuration 162

Leaf – BGP Policy and BGP Update settings 162

Spine - BGP Adjacency and BGP Update settings 163

SuperSpine - BGP Adjacency and BGP Update settings 166

Verification 170

Complexity Chart of Hybrid-ASN Design 186

Direct Underlay Peering – Loopback Overlay Peering 186

Chapter 7:  Dual-AS Model with OSPF Underlay 188

Introduction 188

Configuration 189

BGP Adjacency Policy 189

BGP Update Message Modification 189

BGP Loop Prevention Adjustment 190

Verification 192

BGP peering 192

BGP table 192

L2RIB 195

MAC Address Table 196

Complexity Chart of Hybrid-ASN Design with OSPF Underlay 197

Chapter 8:  ESI Multi-Homing 198

Introduction 198

ESI Multihoming Configuration 199

Designated Forwarder fo L2BUM 201

Mass-Withdraw 205

Load-Balancing 213

References 216

Chapter 9:  ECMP process 217

ECMP process 217

Chapter 10: L3-Only Inter-Pod Connection 227

Introduction 227

MPLS Core Underlay Routing with IS-IS. 228

IS-IS Configuration 229

IS-IS Verification 229

MPLS Label Distribution with LDP 231

MPLS LDP Configuration 233

MPLS Verification 233

MPLS Control-Plane Operation - LDP 235

MPLS Data-Plane Operation – Label Switching 236

BGP VPNv4 Peering 238

BGP VPNv4 Configuration 238

BGP VPNv4 Peering Verification 239

BGP L2VPN EVPN Peering 240

BGP VPNv4 Configuration 240

BGP L2VPN EVPN Peering Verification 241

Adding Tenant to Border Leafs 242

Tenant Configuration 242

Verification 244

Control-Plane: End-to-End Route Propagation 244

Data-Plane: Label Switching Path 249

Data-Plane: ICMP Request 251

Appendix A: Chapter 10 device configurations 253