Routing Configuration Guide for Cisco ASR 9000 Series ... · CONTENTS PREFACE Preface xxix...

Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOSXR Release 6.5.xFirst Published: 2019-01-01

Last Modified: 2019-03-01

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C O N T E N T S

Preface xxixP R E F A C EChanges to This Document xxix

Communications, Services, and Additional Information xxix

New and Changed Routing Features 1C H A P T E R 1

New and Changed Routing Features 1

Implementing BGP 3C H A P T E R 2

Prerequisites for Implementing BGP 5

Information About Implementing BGP 5

BGP Functional Overview 5

BGP Router Identifier 6

BGP Maximum Prefix - Discard Extra Paths 7

Restrictions 7

BGP Default Limits 7

BGP Next Hop Tracking 8

Scoped IPv4/VPNv4 Table Walk 10

Reordered Address Family Processing 10

New Thread for Next-Hop Processing 10

show, clear, and debug Commands 10

Autonomous System Number Formats in BGP 11

2-byte Autonomous System Number Format 11

4-byte Autonomous System Number Format 11

as-format Command 11

BGP Configuration 11

Configuration Modes 11

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Neighbor Submode 16

Configuration Templates 17

Template Inheritance Rules 18

Viewing Inherited Configurations 23

No Default Address Family 28

Neighbor Address Family Combinations 28

Routing Policy Enforcement 28

Table Policy 30

Update Groups 30

BGP Update Generation and Update Groups 31

BGP Update Group 31

BGP Cost Community 31

How BGP Cost Community Influences the Best Path Selection Process 31

Cost Community Support for Aggregate Routes and Multipaths 32

Influencing Route Preference in a Multiexit IGP Network 34

BGP Cost Community Support for EIGRP MPLS VPN PE-CE with Back-door Links 34

Adding Routes to the Routing Information Base 35

BGP DMZ Aggregate Bandwidth 36

Configuring BGP DMZ Aggregate Bandwidth: Example 37

Configuring Policy-based Link Bandwidth: Example 37

64-ECMP Support for BGP 38

BGP Best Path Algorithm 38

Comparing Pairs of Paths 38

Order of Comparisons 40

Best Path Change Suppression 41

Administrative Distance 41

Multiprotocol BGP 43

Route Dampening 45

Minimizing Flapping 45

BGP Routing Domain Confederation 46

BGP Route Reflectors 46

BGP Optimal Route Reflector 49

Use Case 50

RPL - if prefix is-best-path/is-best-multipath 53

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Contents

Remotely Triggered Blackhole Filtering with RPL Next-hop Discard Configuration 54

Configuring Destination-based RTBH Filtering 54

Verification 56

Default Address Family for show Commands 56

TCP Maximum Segment Size 57

Per Neighbor TCP MSS 57

MPLS VPN Carrier Supporting Carrier 57

BGP Keychains 58

BGP Nonstop Routing 58

BGP Local Label Retention 60

Command Line Interface (CLI) Consistency for BGP Commands 60

BGP Additional Paths 60

iBGP Multipath Load Sharing 60

BGP Selective Multipath 61

Accumulated Interior Gateway Protocol Attribute 63

Per VRF and Per CE Label for IPv6 Provider Edge 63

IPv4 BGP-Policy Accounting on Cisco ASR 9000's A9K-SIP-700 63

IPv6 Unicast Routing on Cisco ASR 9000's A9K-SIP-700 64

IPv6 uRPF Support on Cisco ASR 9000's A9K-SIP-700 64

Remove and Replace Private AS Numbers from AS Path in BGP 64

Selective VRF Download 65

Line Card Roles and Filters in Selective VRF Download 65

Selective VRF Download Disable 66

Calculating Routes Downloaded to Line Card with or without SVD 66

BGP Accept Own 68

BGP DMZ Link Bandwidth for Unequal Cost Recursive Load Balancing 70

BFD Multihop Support for BGP 70

BGP Multi-Instance and Multi-AS 70

BGP Prefix Origin Validation Based on RPKI 71

Configuring RPKI Cache-server 71

Configuring RPKI Prefix Validation 73

Configuring RPKI Bestpath Computation 74

BGP 3107 PIC Updates for Global Prefixes 75

BGP Prefix Independent Convergence for RIB and FIB 76

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BGP Update Message Error Handling 77

BGP Attribute Filtering 77

BGP Attribute Filter Actions 77

BGP Error Handling and Attribute Filtering Syslog Messages 78

BGP Link-State 78

BGP Permanent Network 79

BGP-RIB Feedback Mechanism for Update Generation 79

BGP VRF Dynamic Route Leaking 80

EVPN Default VRF Route Leaking 80

EVPN Default VRF Route Leaking on the DCI for Internet Connectivity 82

Leaking Routes from Default-VRF to Data Center-VRF 82

Leaking Routes to Default-VRF from Data Center-VRF 84

EVPN Service VRF Route Leaking 87

EVPN Service VRF Route Leaking on the DCI for Service Connectivity 89

Leaking Routes from Service VRF to Data Center VRF 89

Leaking Routes to Service VRF from Data Center VRF 92

User Defined Martian Check 97

Resilient Per-CE Label Mode 98

Implementing Excessive Punt Flow Trap on BGP and OSPF 98

Information About Excessive Punt Flow Trap 99

Restrictions for Implementing EPFT 99

Enable Excessive Punt Flow Trap Processing 99

BGP Multipath Enhancements 100

MVPN with BGP SAFI-2 and SAFI-129 101

Overview of BGP Monitoring Protocol 102

BGPMultiple Cluster IDs 103

Benefit of Multiple Cluster IDs Per Route Reflector 103

How a CLUSTER_LIST Attribute is Used 104

Behaviors When Disabling Client-to-Client Route Reflection 104

Configure a Cluster ID per Neighbor 105

Disable Client-to-Client Reflection for Specified Cluster IDs 107

How to Implement BGP 108

Enabling BGP Routing 108

Configuring Multiple BGP Instances for a Specific Autonomous System 110

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Configuring a Routing Domain Confederation for BGP 111

Resetting an eBGP Session Immediately Upon Link Failure 112

Logging Neighbor Changes 112

Adjusting BGP Timers 112

Changing the BGP Default Local Preference Value 113

Configuring the MED Metric for BGP 114

Configuring BGP Weights 115

Tuning the BGP Best-Path Calculation 116

Indicating BGP Back-door Routes 117

Configuring Aggregate Addresses 118

Redistributing iBGP Routes into IGP 119

Configuring Discard Extra Paths 120

Configuring Per Neighbor TCP MSS 121

Disabling Per Neighbor TCP MSS 123

Redistributing Prefixes into Multiprotocol BGP 125

Configuring BGP Route Dampening 127

Applying Policy When Updating the Routing Table 131

Setting BGP Administrative Distance 132

Configuring a BGP Neighbor Group and Neighbors 133

Configuring a Route Reflector for BGP 135

Configuring BGP Route Filtering by Route Policy 136

Configuring BGP Attribute Filtering 138

Configuring BGP Next-Hop Trigger Delay 139

Disabling Next-Hop Processing on BGP Updates 140

Configuring BGP Community and Extended-Community Advertisements 141

Configuring the BGP Cost Community 143

Configuring Software to Store Updates from a Neighbor 146

BGP Persistence 147

BGP Persistence Configuration: Example 148

BGP Graceful Maintenance 148

Restrictions for BGP Graceful Maintenance 148

Graceful Maintenance Operation 149

Inter Autonomous System 150

No Automatic Shutdown 150

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When to Shut Down After Graceful Maintenance 150

Activate Graceful Maintenance under BGP Router (All Neighbors) 150

Direct Router to Reduce Route Preference 153

Bring Router or Link Back into Service 155

Show Command Outputs to Verify BGP Graceful Maintenance 155

Flow-tag propagation 156

Restrictions for flow-tag propagation 157

Source and destination-based flow tag 157

Configure Source and Destination-based Flow Tag 157

Configuring a VPN Routing and Forwarding Instance in BGP 158

Defining Virtual Routing and Forwarding Tables in Provider Edge Routers 159

Configuring the Route Distinguisher 160

Configuring PE-PE or PE-RR Interior BGP Sessions 162

Configuring Route Reflector to Hold Routes That Have a Defined Set of RT Communities 164

Configuring BGP as a PE-CE Protocol 165

Redistribution of IGPs to BGP 169

Configuring Keychains for BGP 170

Disabling a BGP Neighbor 171

Neighbor Capability Suppression 172

Configuration: 172

BGP Dynamic Neighbors 173

Configuring BGP Dynamic Neighbors using Address Range 173

Remote AS 175

Maximum-peers and Idle-watch timeout 176

Resetting Neighbors Using BGP Inbound Soft Reset 177

Resetting Neighbors Using BGP Outbound Soft Reset 178

Resetting Neighbors Using BGP Hard Reset 179

Clearing Caches, Tables, and Databases 179

Displaying System and Network Statistics 180

Displaying BGP Process Information 182

Monitoring BGP Update Groups 183

Configuring BGP Nonstop Routing 184

Disable BGP Nonstop Routing 184

Re-enable BGP Nonstop Routing 185

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Installing Primary Backup Path for Prefix Independent Convergence (PIC) 185

Retaining Allocated Local Label for Primary Path 186

Configuring BGP Additional Paths 187

Configuring iBGP Multipath Load Sharing 189

Originating Prefixes with AiGP 189

Configuring BGP Accept Own 191

Configuring BGP Link-State 192

Configuring BGP Link-state 192

Configuring Domain Distinguisher 193

Configuring BGP Permanent Network 194

Configuring BGP Permanent Network 194

How to Advertise Permanent Network 196

Enabling BGP Unequal Cost Recursive Load Balancing 197

Configuring VRF Dynamic Route Leaking 199

Enabling Selective VRF Download 200

Disabling Selective VRF Download 202

Configuring Resilient Per-CE Label Mode 203

Configuring Resilient Per-CE Label Mode Under VRF Address Family 203

Configuring Resilient Per-CE Label Mode Using a Route-Policy 205

Configuring BGP Large Communities 207

Configuration Examples for Implementing BGP 212

Enabling BGP: Example 212

Displaying BGP Update Groups: Example 213

BGP Neighbor Configuration: Example 214

BGP Confederation: Example 214

BGP Route Reflector: Example 216

BGP Nonstop Routing Configuration: Example 216

Primary Backup Path Installation: Example 217

Allocated Local Label Retention: Example 217

iBGP Multipath Loadsharing Configuration: Example 217

Discard Extra Paths Configuration: Example 217

Displaying Discard Extra Paths Information: Example 218

Advertising IPv4 NLRI with IPv6 Next Hops in MP-BGP Networks 219

Configure Per Neighbor TCP MSS: Examples 224

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Verify Per Neighbor TCP MSS: Examples 226

Originating Prefixes With AiGP: Example 228

BGP Accept Own Configuration: Example 228

BGP Unequal Cost Recursive Load Balancing: Example 229

VRF Dynamic Route Leaking Configuration: Example 231

Resilient Per-CE Label Mode Configuration: Example 232

Configuring Resilient Per-CE Label Mode Under VRF Address Family: Example 232

Configuring Resilient Per-CE Label Mode Using a Route-Policy: Example 232

Flow-tag propagation 232

Restrictions for Flow-Tag Propagation 233

Where to Go Next 233

Additional References 233

Implementing BGP Flowspec 237C H A P T E R 3

BGP Flow Specification 237

Limitations 238

BGP Flowspec Conceptual Architecture 238

Information About Implementing BGP Flowspec 239

Flow Specifications 239

Supported Matching Criteria and Actions 240

Traffic Filtering Actions 244

BGP Flowspec Client-Server (Controller) Model and Configuration with ePBR 245

Configuring BGP Flowspec with ePBR 246

Enable BGP Flowspec 247

Configure a Class Map 248

Configure a Policy Map 250

Link BGP Flowspec to ePBR Policies 251

Verify BGP Flowspec 255

Preserving Redirect Nexthop 257

Validate BGP Flowspec 258

Disabling BGP Flowspec 259

Disable Flowspec Redirect and Validation 260

Configuration Examples for Implementing BGP Flowspec 261

Flowspec Rule Configuration 261

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Drop Packet Length 262

Redirect traffic and rate-limit: Example 262

Redirect Traffic from Global to VRF (vrf1) 263

Remark DSCP 263

Additional References for BGP Flowspec 263

Implementing BFD 265C H A P T E R 4

Prerequisites for Implementing BFD 267

Restrictions for Implementing BFD 268

Information About BFD 269

Differences in BFD in Cisco IOS XR Software and Cisco IOS Software 269

BFD Multipath Sessions Support on nV Edge System 270

BFD Modes of Operation 270

BFD Packet Information 271

BFD Source and Destination Ports 271

BFD Packet Intervals and Failure Detection 271

Priority Settings for BFD Packets 275

BFD for IPv4 276

BFD for IPv6 277

BFD on Bundled VLANs 277

BFD Over Member Links on Link Bundles 278

Overview of BFD State Change Behavior on Member Links and Bundle Status 279

BFD Multipath Sessions 280

BFD for MultiHop Paths 281

Setting up BFD Multihop 281

BFD over MPLS Traffic Engineering LSPs 281

Echo Timer configuration for BFD on Bundle Interfaces 282

Bidirectional Forwarding Detection over Generic Routing Encapsulation 283

Configure Bidirectional Forwarding Detection over Generic Routing Encapsulation 283

Bidirectional Forwarding Detection IPv6 Multihop 286

BFD over Pseudowire Headend 287

BFD over Satellite Interfaces 287

BFD over IRB 288

BFD over Bundle Per-Member Link 288

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BFD over Bundles CISCO/IETF Mode Support on a Per Bundle Basis 289

BFD Dampening 289

BFD Hardware Offload 290

BFD Object Tracking 291

How to Configure BFD 291

BFD Configuration Guidelines 291

Configuring BFD Under a Dynamic Routing Protocol or Using a Static Route 292

Enabling BFD on a BGP Neighbor 292

Enabling BFD for OSPF on an Interface 293

Enabling BFD for OSPFv3 on an Interface 295

Enabling BFD on a Static Route 297

Enabling BFD on a IPv6 Static Route 298

Configuring BFD on Bundle Member Links 298

Prerequisites for Configuring BFD on Bundle Member Links 298

Specifying the BFD Destination Address on a Bundle 298

Enabling BFD Sessions on Bundle Members 299

Configuring the Minimum Thresholds for Maintaining an Active Bundle 300

Configuring BFD Packet Transmission Intervals and Failure Detection Times on a Bundle 301

Configuring Allowable Delays for BFD State Change Notifications Using Timers on a Bundle302

Configure BFD over Bundles CISCO/IETF Mode Support on a Per Bundle Basis 303

Configuring BFD over Bundle for Hardware Offload 305

Enabling Echo Mode to Test the Forwarding Path to a BFD Peer 307

Overriding the Default Echo Packet Source Address 308

Specifying the Echo Packet Source Address Globally for BFD 308

Specifying the Echo Packet Source Address on an Individual Interface or Bundle 309

Configuring BFD Session Teardown Based on Echo Latency Detection 310

Delaying BFD Session Startup Until Verification of Echo Path and Latency 310

Disabling Echo Mode 312

Disabling Echo Mode on a Router 312

Disabling Echo Mode on an Individual Interface or Bundle 313

Minimizing BFD Session Flapping Using BFD Dampening 313

Enabling and Disabling IPv6 Checksum Support 314

Enabling and Disabling IPv6 Checksum Calculations for BFD on a Router 314

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Enabling and Disabling IPv6 Checksum Calculations for BFD on an Individual Interface orBundle 315

Clearing and Displaying BFD Counters 316

BFD IPv6 in Bundle Manager Domain 317

Configuration: 317

Configuring BFD IPv6 Multihop 318

Configuring BFD IPv6 Multihop for eBGP Neighbors 318

Configuring BFD IPv6 Multihop for iBGP Neighbors 319

Configuring BFD over MPLS Traffic Engineering LSPs 320

Enabling BFD Parameters for BFD over TE Tunnels 320

Configuring BFD Bring up Timeout 321

Configuring BFD Dampening for TE Tunnels 322

Configuring Periodic LSP Ping Requests 323

Configuring BFD at the Tail End 324

Configuring BFD over LSP Sessions on Line Cards 325

Configuring BFD Object Tracking: 326

Configuration Examples for Configuring BFD 327

BFD Over BGP: Example 327

BFD Over OSPF: Examples 327

BFD Over Static Routes: Examples 328

BFD on Bundled VLANs: Example 328

BFD Over Bridge Group Virtual Interface: Example 329

BFD on Bundle Member Links: Examples 331

Echo Packet Source Address: Examples 332

Echo Latency Detection: Examples 332

Echo Startup Validation: Examples 333

BFD Echo Mode Disable: Examples 333

BFD Dampening: Examples 334

BFD IPv6 Checksum: Examples 334

BFD Peers on Routers Running Cisco IOS and Cisco IOS XR Software: Example 335

BFD Over Bundle Hardware Offload: Example 335

BFD Over Bridge Group Virtual Interface: Example 336

Configuring BFD IPv6 Multihop: Examples 338

BFD over MPLS TE LSPs: Examples 339

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BFD over MPLS TE Tunnel Head-end Configuration: Example 339

BFD over MPLS TE Tunnel Tail-end Configuration: Example 339



Related Documents 340

Standards 340

RFCs 340

MIBs 340

Technical Assistance 341

Implementing EIGRP 343C H A P T E R 5

Prerequisites for Implementing EIGRP 344

Restrictions for Implementing EIGRP 344

Information About Implementing EIGRP 344

EIGRP Functional Overview 344

EIGRP Features 345

EIGRP Components 345

EIGRP Configuration Grouping 346

EIGRP Configuration Modes 346

EIGRP Interfaces 347

Redistribution for an EIGRP Process 347

Metric Weights for EIGRP Routing 348

Mismatched K Values 348

Goodbye Message 349

Percentage of Link Bandwidth Used for EIGRP Packets 349

Floating Summary Routes for an EIGRP Process 349

Split Horizon for an EIGRP Process 351

Adjustment of Hello Interval and Hold Time for an EIGRP Process 351

Stub Routing for an EIGRP Process 352

Route Policy Options for an EIGRP Process 353

EIGRP Layer 3 VPN PE-CE Site-of-Origin 354

Router Interoperation with the Site-of-Origin Extended Community 354

Route Manipulation using SoO match condition 354

EIGRP v4/v6 Authentication Using Keychain 356

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EIGRP Wide Metric Computation 356

EIGRP Multi-Instance 357

EIGRP Support for BFD 357

How to Implement EIGRP 357

Enabling EIGRP Routing 357

Configuring Route Summarization for an EIGRP Process 359

Redistributing Routes for EIGRP 360

Creating a Route Policy and Attaching It to an EIGRP Process 362

Configuring Stub Routing for an EIGRP Process 363

Configuring EIGRP as a PE-CE Protocol 364

Redistributing BGP Routes into EIGRP 366

Monitoring EIGRP Routing 367

Configuring an EIGRP Authentication Keychain 370

Configuring an Authentication Keychain for an IPv4/IPv6 Interface on a Default VRF 370

Configuring an Authentication Keychain for an IPv4/IPv6 Interface on a Nondefault VRF 371

Configuring unicast neighbors 372

Remote Neighbor Session Policy 372

Understanding Neighbor Terms 373

Remote Unicast-Listen (Point-to-Point) Neighbors 374

Restrictions for remote neighbors 374

Inheritance and precedence of the remote neighbor configurations 374

How to configure remote unicast neighbors 375

Configuration Examples for Implementing EIGRP 376

Configuring a Basic EIGRP Configuration: Example 376

Configuring an EIGRP Stub Operation: Example 377

Configuring an EIGRP PE-CE Configuration with Prefix-Limits: Example 377

Configuring an EIGRP Authentication Keychain: Example 377


Implementing IS-IS 381C H A P T E R 6

Prerequisites for Implementing IS-IS 381

Restrictions for Implementing IS-IS 381

Information About Implementing IS-IS 382

IS-IS Functional Overview 382

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Key Features Supported in the Cisco IOS XR IS-IS Implementation 382

IS-IS Configuration Grouping 383

IS-IS Configuration Modes 383

Router Configuration Mode 383

Router Address Family Configuration Mode 383

Interface Configuration Mode 383

Interface Address Family Configuration Mode 383

IS-IS Interfaces 384

Multitopology Configuration 384

IPv6 Routing and Configuring IPv6 Addressing 384

Limit LSP Flooding 384

Flood Blocking on Specific Interfaces 385

Mesh Group Configuration 385

Maximum LSP Lifetime and Refresh Interval 385

Minimum Remaining Lifetime 385

Single-Topology IPv6 Support 386

Multitopology IPv6 for IS-IS 386

IS-IS Authentication 387

Purge Originator Identification TLV for IS-IS 387

Nonstop Forwarding 388

ISIS NSR 389

Configuring IS-IS Adjacency Stagger 389

Multi-Instance IS-IS 390

Multiprotocol Label Switching Traffic Engineering 390

Overload Bit on Router 390

Overload Bit Configuration During Multitopology Operation 391

IS-IS Overload Bit Avoidance 391

Default Routes 391

Attached Bit on an IS-IS Instance 391

IS-IS Support for Route Tags 392

Multicast-Intact Feature 392

Multicast Topology Support Using IS-IS 392

MPLS Label Distribution Protocol IGP Synchronization 393

MPLS LDP-IGP Synchronization Compatibility with LDP Graceful Restart 393

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MPLS LDP-IGP Synchronization Compatibility with IGP Nonstop Forwarding 393

Label Distribution Protocol IGP Auto-configuration 393

MPLS TE Forwarding Adjacency 394

MPLS TE Interarea Tunnels 394

IP Fast Reroute 394

Unequal Cost Multipath Load-balancing for IS-IS 394

Enabling IS-IS and Configuring Level 1 or Level 2 Routing 395

Configuring Single Topology for IS-IS 397

Configuring Multitopology Routing 401

Restrictions for Configuring Multitopology Routing 401

Information About Multitopology Routing 401

Configuring a Global Topology and Associating It with an Interface 401

Enabling an IS-IS Topology 403

Placing an Interface in a Topology in IS-IS 403

Configuring a Routing Policy 404

Configuring Multitopology for IS-IS 405

Controlling LSP Flooding for IS-IS 405

Configuring Nonstop Forwarding for IS-IS 409

Configuring ISIS-NSR 410

Configuring Authentication for IS-IS 412

Configuring Keychains for IS-IS 414

Configuring MPLS Traffic Engineering for IS-IS 415

Tuning Adjacencies for IS-IS 417

Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration 419

Customizing Routes for IS-IS 421

Configuring MPLS LDP IS-IS Synchronization 424

Enabling Multicast-Intact 425

Tagging IS-IS Interface Routes 426

Setting the Priority for Adding Prefixes to the RIB 427

Configuring IP Fast Reroute Loop-free Alternate 428

Configuring IS-IS Overload Bit Avoidance 430

Configuring Global Weighted SRLG Protection 430

ISIS Link Group 432

Configure Link Group Profile 433

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Configure Link Group Interface 435

Configuration Examples for Implementing IS-IS 436

Configuring Single-Topology IS-IS for IPv6: Example 436

Configuring Multitopology IS-IS for IPv6: Example 437

Redistributing IS-IS Routes Between Multiple Instances: Example 437

Tagging Routes: Example 438

Configuring IS-IS Overload Bit Avoidance: Example 438

Example: Configuring IS-IS To Handle Router Overload 438



Implementing OSPF 447C H A P T E R 7

Prerequisites for Implementing OSPF 448

Information About Implementing OSPF 449

OSPF Functional Overview 449

Key Features Supported in the Cisco IOS XR Software OSPF Implementation 450

Comparison of Cisco IOS XR Software OSPFv3 and OSPFv2 451

OSPF Hierarchical CLI and CLI Inheritance 451

OSPF Routing Components 452

Autonomous Systems 452

Areas 452

Routers 453

OSPF Process and Router ID 454

Supported OSPF Network Types 455

Route Authentication Methods for OSPF 455

Plain Text Authentication 455

MD5 Authentication 455

HMAC-SHA Authentication 455

Authentication Strategies 456

Key Rollover 456

Neighbors and Adjacency for OSPF 456

OSPF strict-mode Support for BFD Dampening 457

Enabling strict-mode 457

BFD strict-mode: Example 458

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OSPF FIB Download Notification 459

Designated Router (DR) for OSPF 459

Default Route for OSPF 460

Link-State Advertisement Types for OSPF Version 2 460

Link-State Advertisement Types for OSPFv3 461

Virtual Link and Transit Area for OSPF 462

Passive Interface 462

OSPFv2 Sham Link Support for MPLS VPN 463

OSPFv3 Sham Link Support for MPLS VPN 464

Graceful Restart Procedure over the Sham-link 464

ECMP and OSPFv3 Sham-link 465

OSPF SPF Prefix Prioritization 465

Route Redistribution for OSPF 466

OSPF Shortest Path First Throttling 466

Nonstop Forwarding for OSPF Version 2 467

Graceful Shutdown for OSPFv3 468

Modes of Graceful Restart Operation 468

Graceful Restart Requirements and Restrictions 470

Warm Standby and Nonstop Routing for OSPF Version 2 471

Warm Standby for OSPF Version 3 471

Multicast-Intact Support for OSPF 472

Load Balancing in OSPF Version 2 and OSPFv3 472

Configure Prefix Suppression for OSPF 472

Configure Prefix Suppression for OSPFv3 477

Multi-Area Adjacency for OSPF Version 2 482

Label Distribution Protocol IGP Auto-configuration for OSPF 483

OSPF Authentication Message Digest Management 483

GTSM TTL Security Mechanism for OSPF 483

Path Computation Element for OSPFv2 484

OSPF IP Fast Reroute Loop Free Alternate 484

Management Information Base (MIB) for OSPFv3 484

VRF-lite Support for OSPFv2 485

OSPFv3 Timers Link-state Advertisements and Shortest Path First Throttle Default Values Update485

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Unequal Cost Multipath Load-balancing for OSPF 485

How to Implement OSPF 486

Enabling OSPF 486

Configuring Stub and Not-So-Stubby Area Types 488

Configuring Neighbors for Nonbroadcast Networks 490

Configuring Authentication at Different Hierarchical Levels for OSPF Version 2 493

Controlling the Frequency That the Same LSA Is Originated or Accepted for OSPF 495

Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF 497

Examples 500

Summarizing Subnetwork LSAs on an OSPF ABR 500

Redistribute Routes into OSPF 502

Configuring OSPF Shortest Path First Throttling 504

Examples 506

Configuring Nonstop Forwarding Specific to Cisco for OSPF Version 2 506

Configuring OSPF Version 2 for MPLS Traffic Engineering 508

Examples 510

Configuring OSPFv3 Graceful Restart 512

Displaying Information About Graceful Restart 513

Configuring an OSPFv2 Sham Link 514

Configuring OSPF SPF Prefix Prioritization 517

Enabling Multicast-intact for OSPFv2 518

Associating Interfaces to a VRF 519

Configuring OSPF as a Provider Edge to Customer Edge (PE-CE) Protocol 520

Creating Multiple OSPF Instances (OSPF Process and a VRF) 522

Configuring Multi-area Adjacency 523

Configuring Label Distribution Protocol IGP Auto-configuration for OSPF 525

Configuring LDP IGP Synchronization: OSPF 525

Configuring Authentication Message Digest Management for OSPF 526

Examples 528

Configuring Generalized TTL Security Mechanism (GTSM) for OSPF 529

Examples 531

Verifying OSPF Configuration and Operation 531

Configuring IP Fast Reroute Loop-free Alternate 533

Enabling IPFRR LFA 534

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Contents

Excluding an Interface From IP Fast Reroute Per-link Computation 534

Enabling OSPF Interaction with SRMS Server 535

Configuration Examples for Implementing OSPF 537

Cisco IOS XR Software for OSPF Version 2 Configuration: Example 537

CLI Inheritance and Precedence for OSPF Version 2: Example 538

MPLS TE for OSPF Version 2: Example 539

ABR with Summarization for OSPFv3: Example 539

ABR Stub Area for OSPFv3: Example 540

ABR Totally Stub Area for OSPFv3: Example 540

Configuring OSPF SPF Prefix Prioritization: Example 540

Route Redistribution for OSPFv3: Example 541

Virtual Link Configured Through Area 1 for OSPFv3: Example 542

Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example 542

VPN Backbone and Sham Link Configured for OSPF Version 2: Example 543



Implementing IP Fast Reroute Loop-Free Alternate 549C H A P T E R 8

Prerequisites for IPv4/IPv6 Loop-Free Alternate Fast Reroute 549

Restrictions for Loop-Free Alternate Fast Reroute 549

IS-IS and IP FRR 550

Repair Paths 550

LFA Overview 551

LFA Calculation 551

Interaction Between RIB and Routing Protocols 551

Configuring Fast Reroute Support 552

Configuring IPv4 Loop-Free Alternate Fast Reroute Support: Example 554


Implementing and Monitoring RIB 557C H A P T E R 9

Prerequisites for Implementing RIB 558

Information About RIB Configuration 558

Overview of RIB 558

RIB Data Structures in BGP and Other Protocols 558

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Contents

RIB Administrative Distance 558

RIB Support for IPv4 and IPv6 559

RIB Statistics 559

IPv6 Provider Edge IPv6 and IPv6 VPN Provider Edge Transport over MPLS 560

RIB Quarantining 560

Route and Label Consistency Checker 561

How to Deploy and Monitor RIB 561

Verifying RIB Configuration Using the Routing Table 562

Verifying Networking and Routing Problems 562

Disabling RIB Next-hop Dampening 564

Configuring RCC and LCC 565

Enabling RCC and LCC On-demand Scan 565

Enabling RCC and LCC Background Scan 566

BGP-RIB Feedback Mechanism for Update Generation 567

Configuration Examples for RIB Monitoring 567

Output of show route Command: Example 567

Output of show route backup Command: Example 568

Output of show route best-local Command: Example 568

Output of show route connected Command: Example 568

Output of show route local Command: Example 569

Output of show route longer-prefixes Command: Example 569

Output of show route next-hop Command: Example 569

Enabling RCC and LCC: Example 570



Implementing RIP 573C H A P T E R 1 0

Prerequisites for Implementing RIP 574

Information About Implementing RIP 574

RIP Functional Overview 574

Split Horizon for RIP 575

Route Timers for RIP 575

Route Redistribution for RIP 575

Default Administrative Distances for RIP 576

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Contents

Routing Policy Options for RIP 577

Authentication Using Keychain in RIP 577

In-bound RIP Traffic on an Interface 578

Out-bound RIP Traffic on an Interface 579

How to Implement RIP 579

Enabling RIP 579

Customizing RIP 581

Control Routing Information 582

Creating a Route Policy for RIP 584

Configuring RIP Authentication Keychain 585

Configuring RIP Authentication Keychain for IPv4 Interface on a Non-default VRF 585

Configuring RIP Authentication Keychain for IPv4 Interface on Default VRF 587

Configuration Examples for Implementing RIP 588

Configuring a Basic RIP Configuration: Example 588

Configuring RIP on the Provider Edge: Example 588

Adjusting RIP Timers for each VRF Instance: Example 588

Configuring Redistribution for RIP: Example 589

Configuring Route Policies for RIP: Example 590

Configuring Passive Interfaces and Explicit Neighbors for RIP: Example 590

Controlling RIP Routes: Example 591

Configuring RIP Authentication Keychain: Example 591


Implementing Routing Policy 593C H A P T E R 1 1

Prerequisites for Implementing Routing Policy 594

Restrictions for Implementing Routing Policy 594

Information About Implementing Routing Policy 595

Routing Policy Language 595

Routing Policy Language Overview 595

Routing Policy Language Structure 596

Routing Policy Language Components 605

Routing Policy Language Usage 606

Routing Policy Configuration Basics 608

Policy Definitions 608

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Contents

Parameterization 609

Parameterization at Attach Points 610

Global Parameterization 610

Semantics of Policy Application 611

Boolean Operator Precedence 611

Multiple Modifications of the Same Attribute 611

When Attributes Are Modified 612

Default Drop Disposition 613

Control Flow 613

Policy Verification 614

Policy Statements 615

Remark 615

Disposition 616

Action 618

If 618

Boolean Conditions 619

apply 620

Attach Points 620

BGP Policy Attach Points 621

OSPF Policy Attach Points 646

OSPFv3 Policy Attach Points 650

IS-IS Policy Attach Points 652

EIGRP Policy Attach Points 654

RIP Policy Attach Points 658

PIM Policy Attach Points 660

Nondestructive Editing of Routing Policy 660

Attached Policy Modification 660

Nonattached Policy Modification 661

Editing Routing Policy Configuration Elements 661

Hierarchical Policy Conditions 663

Apply Condition Policies 663

Nested Wildcard Apply Policy 666

Wildcards for Route Policy Sets 667

Use Wildcards For Routing Policy Sets 667

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Contents

VRF Import Policy Enhancement 671

Flexible L3VPN Label Allocation Mode 671

Match Aggregated Route 672

Set Administrative Distance 672

How to Implement Routing Policy 672

Defining a Route Policy 672

Attaching a Routing Policy to a BGP Neighbor 673

Modifying a Routing Policy Using a Text Editor 674

Configuration Examples for Implementing Routing Policy 675

Routing Policy Definition: Example 675

Simple Inbound Policy: Example 676

Modular Inbound Policy: Example 677

Use Wildcards For Routing Policy Sets 678

VRF Import Policy Configuration: Example 682


Implementing Static Routes 685C H A P T E R 1 2

Prerequisites for Implementing Static Routes 685

Restrictions for Implementing Static Routes 686

Information About Implementing Static Routes 686

Static Route Functional Overview 686

Default Administrative Distance 686

Directly Connected Routes 687

Recursive Static Routes 687

Fully Specified Static Routes 688

Floating Static Routes 688

Default VRF 688

IPv4 and IPv6 Static VRF Routes 688

Dynamic ECMP 689

How to Implement Static Routes 689

Configure Static Route 689

Configure Floating Static Route 690

Configure Static Routes Between PE-CE Routers 692

Change Maximum Number of Allowable Static Routes 693

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Associate VRF with a Static Route 694

Configuration Examples 695

Configuring Traffic Discard: Example 695

Configuring a Fixed Default Route: Example 696

Configuring a Floating Static Route: Example 696

Configure Native UCMP for Static Routing 696

Configuring a Static Route Between PE-CE Routers: Example 697


Implementing RCMD 699C H A P T E R 1 3

Route Convergence Monitoring and Diagnostics 699

Configuring Route Convergence Monitoring and Diagnostics 700

Route Convergence Monitoring and Diagnostics Prefix Monitoring 702

Route Convergence Monitoring and Diagnostics OSPF Type 3/5/7 Link-state AdvertisementsMonitoring 703

Enabling RCMD Monitoring for IS-IS Prefixes 703

Enable RCMD Monitoring for OSPF Prefixes 704

Enabling RCMD Monitoring for Type 3/5/7 OSPF LSAs 705

Enabling RCMD Monitoring for IS-IS Prefixes: Example 706

Enabling RCMD Monitoring for OSPF Prefixes: Example 706

Enabling RCMD Monitoring for Type 3/5/7 OSPF LSAs: Example 706

Implementing UCMP 709C H A P T E R 1 4

ECMP vs. UCMP Load Balancing 710

UCMP Minimum Integer Ratio 710

Configuring IS-IS With Weight 711

Configuring IS-IS With Metric 712

Configuring BGP With Weights 713

Configuring TE Tunnel With Weights 714

Policy-Based Tunnel Selection 715

Implementing Data Plane Security 729C H A P T E R 1 5

Information about Data Plane Security 729

Source RLOC Decapsulation Filtering 729

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Contents

EID Instance Membership Distribution 730

Map-Server Membership Gleaning and Distribution 731

Decapsulation Filtering on (P)xTRs 733

TCP-based Reliable Transport Sessions 734

How to Implement Data Plane Security 734

Enable Source RLOC-based Decapsulation Filtering 734

Create, Maintain and Distribute Decapsulation Filter Lists 738

Add or Override Decapsulation Filter List 739

Reset LISP TCP Reliable Transport Session 740

Verify Data Plane Security Configurations 740


Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxxvii

Contents

Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxxviii

Contents

Preface

From Release 6.1.2 onwards, Cisco introduces support for the 64-bit Linux-based IOS XR operating system.Extensive feature parity is maintained between the 32-bit and 64-bit environments. Unless explicitly markedotherwise, the contents of this document are applicable for both the environments. For more details on CiscoIOS XR 64 bit, refer to the Release Notes for Cisco ASR 9000 Series Routers, Release 6.1.2 document.

The Routing Configuration Guide for Cisco ASR 9000 Series Routers preface contains these sections:

Changes to This Document, on page xxix Communications, Services, and Additional Information, on page xxix

Changes to This DocumentThis table lists the technical changes made to this document since it was first released.

Table 1: Changes to This Document

SummaryDate

Initial release of this document.January 2019

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Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxxx

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C H A P T E R 1New and Changed Routing Features

This table summarizes the new and changed feature information for the Routing Configuration Guide forCisco ASR 9000 Series Routers, and tells you where they are documented.

New and Changed Routing Features, on page 1

New and Changed Routing FeaturesTable 2: Routing Features Added or Modified in IOS XR Release 6.5.x

Where DocumentedChanged in ReleaseDescriptionFeature

See MinimumRemaining Lifetime,on page 385 section inImplementingIS-ISchapter.

Release 6.5.1This feature wasintroduced.

Minimum RemainingLifetime for IS-IS

See CustomizingRoutes for IS-IS, onpage 421 section inImplementing IS-ISchapter.


IS-IS Distribute List

See Purge OriginatorIdentification TLV forIS-IS section inImplementing IS-ISchapter.


Purge OriginatorIdentification TLV forIS-IS

ConfiguringAuthenticationMessage DigestManagement forOSPF, on page 526


OSPFAuthenticationwithKeychain

Implementing IS-ISchapter.


Configuring GlobalWeighted SRLGProtection

Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.x1

Where DocumentedChanged in ReleaseDescriptionFeature

See

BGP SessionAuthentication andIntegrity using TCPAuthentication andOption Overview

section

in Implementing BGPchapter


BGP SessionAuthentication andIntegrity using TCPAuthentication Option


New and Changed Routing FeaturesNew and Changed Routing Features

C H A P T E R 2Implementing BGP

Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-freeinterdomain routing between autonomous systems. An autonomous system is a set of routers under a singletechnical administration. Routers in an autonomous system can use multiple Interior Gateway Protocols (IGPs)to exchange routing information inside the autonomous system and an EGP to route packets outside theautonomous system.

This module provides the conceptual and configuration information for BGP on Cisco IOS XR software.

For more information about BGP and complete descriptions of the BGP commands listed in this module, seeRelated Documents, on page 233 section of this module. To locate documentation for other commands thatmight appear while performing a configuration task, search online in the Cisco ASR 9000 Series Routersoftware master command index.

Note

Feature History for Implementing BGP

ModificationRelease

This feature was introduced.Release 3.7.2

The following features were supported:

BGP Prefix Independent Convergence Unipath Primary Backup

BGP Local Label Retention

Asplain notation for 4-byte Autonomous System Number

BGP Nonstop Routing

Command Line Interface (CLI) consistency for BGP commands

L2VPN Address Family Configuration Mode

Release 3.9.0


ModificationRelease


BGP Add Path Advertisement

Accumulated iGP (AiGP)

Pre-route

IPv4 BGP-Policy Accounting

IPv6 uRPF

Release 4.0.0

Support for 5000 BGP NSR sessions was addedRelease 4.1.0

The following features were added:

BGP Accept Own

BGP DMZ Link Bandwidth for Unequal Cost Recursive Load Balancing

Release 4.1.1


Selective VRF Download

BGP Multi-Instance/Multi-AS

BFD Multihop Support for BGP

BGP Error Handling

Support for Distributed BGP (bgp distributed speaker) configuration was removed.

Release 4.2.0


BGP 3107 PIC Updates for Global Prefixes

BGP Prefix Independent Convergence for RIB and FIB

BGP Prefix Origin Validation Based on RPKI

Release 4.2.1

The BGP Attribute Filtering feature was added.Release 4.2.3

The BGP-RIB Feedback Mechanism for Update Generation feature was addedRelease 4.3.0

The following features were supported

BGP VRF Dynamic Route Leaking

The label-allocation-mode command is renamed the label mode command.

Release 4.3.1


Per-neighbor Link Bandwidth

Release 4.3.2


Implementing BGP

ModificationRelease


L3VPN iBGP-PE-CE configuration

Source-based flow tag

Discard extra paths

Release 5.3.1


Graceful Maintenance

Per Neighbor TCP MSS

BGP DMZ Aggregate Bandwidth

Release 5.3.2


Excessive Punt Flow Trap Processing

64-ECMP for BGP

Release 6.0.1

Prerequisites for Implementing BGP, on page 5 Information About Implementing BGP, on page 5 Overview of BGP Monitoring Protocol, on page 102 BGPMultiple Cluster IDs, on page 103 How to Implement BGP, on page 108 Configuration Examples for Implementing BGP, on page 212 Flow-tag propagation, on page 232 Where to Go Next, on page 233 Additional References, on page 233

Prerequisites for Implementing BGPYou must be in a user group associated with a task group that includes the proper task IDs. The commandreference guides include the task IDs required for each command. If you suspect user group assignment ispreventing you from using a command, contact your AAA administrator for assistance.

Information About Implementing BGPTo implement BGP, you need to understand the following concepts:

BGP Functional OverviewBGP uses TCP as its transport protocol. Two BGP routers form a TCP connection between one another (peerrouters) and exchange messages to open and confirm the connection parameters.


Implementing BGPPrerequisites for Implementing BGP

BGP routers exchange network reachability information. This information is mainly an indication of the fullpaths (BGP autonomous system numbers) that a route should take to reach the destination network. Thisinformation helps construct a graph that shows which autonomous systems are loop free and where routingpolicies can be applied to enforce restrictions on routing behavior.

Any two routers forming a TCP connection to exchange BGP routing information are called peers or neighbors.BGP peers initially exchange their full BGP routing tables. After this exchange, incremental updates are sentas the routing table changes. BGP keeps a version number of the BGP table, which is the same for all of itsBGP peers. The version number changes whenever BGP updates the table due to routing information changes.Keepalive packets are sent to ensure that the connection is alive between the BGP peers and notificationpackets are sent in response to error or special conditions.

For information on configuring BGP to distribute Multiprotocol Label Switching (MPLS) Layer 3 virtualprivate network (VPN) information, see the Cisco ASR 9000 Series Aggregation Services Router MPLSConfiguration Guide

For information on BGP support for Bidirectional Forwarding Detection (BFD), see theCisco ASR 9000 SeriesAggregation Services Router Interface and Hardware Configuration Guide and the Cisco ASR 9000 SeriesAggregation Services Router Interface and Hardware Command Reference.

Note

BGP Router IdentifierFor BGP sessions between neighbors to be established, BGP must be assigned a router ID. The router ID issent to BGP peers in the OPEN message when a BGP session is established.

BGP attempts to obtain a router ID in the following ways (in order of preference):

By means of the address configured using the bgp router-id command in router configuration mode.

By using the highest IPv4 address on a loopback interface in the system if the router is booted with savedloopback address configuration.

By using the primary IPv4 address of the first loopback address that gets configured if there are not anyin the saved configuration.

If none of these methods for obtaining a router ID succeeds, BGP does not have a router ID and cannot establishany peering sessions with BGP neighbors. In such an instance, an error message is entered in the system log,and the show bgp summary command displays a router ID of 0.0.0.0.

After BGP has obtained a router ID, it continues to use it even if a better router ID becomes available. Thisusage avoids unnecessary flapping for all BGP sessions. However, if the router ID currently in use becomesinvalid (because the interface goes down or its configuration is changed), BGP selects a new router ID (usingthe rules described) and all established peering sessions are reset.

We strongly recommend that the bgp router-id command is configured to prevent unnecessary changes tothe router ID (and consequent flapping of BGP sessions).

Note


Implementing BGPBGP Router Identifier

BGP Maximum Prefix - Discard Extra PathsIOS XR BGP maximum-prefix feature imposes a maximum limit on the number of prefixes that are receivedfrom a neighbor for a given address family. Whenever the number of prefixes received exceeds the maximumnumber configured, the BGP session is terminated, which is the default behavior, after sending a ceasenotification to the neighbor. The session is down until a manual clear is performed by the user. The sessioncan be resumed by using the clear bgp command. It is possible to configure a period after which the sessioncan be automatically brought up by using themaximum-prefix command with the restart keyword. Themaximum prefix limit can be configured by the user. Default limits are used if the user does not configurethe maximum number of prefixes for the address family. For default limits, refer to BGP Default Limits, onpage 7.

Discard Extra Paths

An option to discard extra paths is added to the maximum-prefix configuration. Configuring the discard extrapaths option drops all excess prefixes received from the neighbor when the prefixes exceed the configuredmaximum value. This drop does not, however, result in session flap.

The benefits of discard extra paths option are:

Limits the memory footstamp of BGP.

Stops the flapping of the peer if the paths exceed the set limit.

When the discard extra paths configuration is removed, BGP sends a route-refresh message to the neighborif it supports the refresh capability; otherwise the session is flapped.

On the same lines, the following describes the actions when the maximum prefix value is changed:

If the maximum value alone is changed, a route-refresh message is sourced, if applicable.

If the new maximum value is greater than the current prefix count state, the new prefix states are saved.

If the new maximum value is less than the current prefix count state, then some existing prefixes aredeleted to match the new configured state value.

There is currently no way to control which prefixes are deleted.

For detailed configuration steps, see Configuring Discard Extra Paths, on page 120.

RestrictionsThese restrictions apply to the discard extra paths feature:

When the router drops prefixes, it is inconsistent with the rest of the network, resulting in possible routingloops.

If prefixes are dropped, the standby and active BGP sessions may drop different prefixes. Consequently,an NSR switchover results in inconsistent BGP tables.

The discard extra paths configuration cannot co-exist with the soft reconfig configuration.

BGP Default LimitsCisco IOS XRBGP imposes maximum limits on the number of neighbors that can be configured on the routerand on the maximum number of prefixes that are accepted from a peer for a given address family. This


Implementing BGPBGP Maximum Prefix - Discard Extra Paths

limitation safeguards the router from resource depletion caused by misconfiguration, either locally or on theremote neighbor. The following limits apply to BGP configurations:

The default maximum number of peers that can be configured is 4000. The default can be changed usingthe bgp maximum neighbor command. The limit range is 1 to 15000. Any attempt to configureadditional peers beyond the maximum limit or set the maximum limit to a number that is less than thenumber of peers currently configured will fail.

To prevent a peer from flooding BGP with advertisements, a limit is placed on the number of prefixesthat are accepted from a peer for each supported address family. The default limits can be overriddenthrough configuration of the maximum-prefix limit command for the peer for the appropriate addressfamily. The following default limits are used if the user does not configure the maximum number ofprefixes for the address family:

IPv4 Unicast: 1048576

IPv4 Labeled-unicast: 131072

IPv4 Tunnel: 1048576

IPv6 Unicast: 524288

IPv6 Labeled-unicast: 131072

IPv4 Multicast: 131072

IPv6 Multicast: 131072

IPv4 MVPN: 2097152

VPNv4 Unicast: 2097152

IPv4 MDT: 131072

VPNv6 Unicast: 1048576

L2VPN EVPN: 2097152

A cease notificationmessage is sent to the neighbor and the peering with the neighbor is terminated whenthe number of prefixes received from the peer for a given address family exceeds the maximum limit(either set by default or configured by the user) for that address family.

It is possible that the maximum number of prefixes for a neighbor for a given address family has beenconfigured after the peering with the neighbor has been established and a certain number of prefixeshave already been received from the neighbor for that address family. A cease notification message issent to the neighbor and peering with the neighbor is terminated immediately after the configuration ifthe configured maximum number of prefixes is fewer than the number of prefixes that have already beenreceived from the neighbor for the address family.

BGP Next Hop TrackingBGP receives notifications from the Routing Information Base (RIB) when next-hop information changes(event-driven notifications). BGP obtains next-hop information from the RIB to:

Determine whether a next hop is reachable.

Find the fully recursed IGP metric to the next hop (used in the best-path calculation).


Implementing BGPBGP Next Hop Tracking

Validate the received next hops.

Calculate the outgoing next hops.

Verify the reachability and connectedness of neighbors.

BGP is notified when any of the following events occurs:

Next hop becomes unreachable

Next hop becomes reachable

Fully recursed IGP metric to the next hop changes

First hop IP address or first hop interface change

Next hop becomes connected

Next hop becomes unconnected

Next hop becomes a local address

Next hop becomes a nonlocal address

Reachability and recursed metric events trigger a best-path recalculation.Note

Event notifications from the RIB are classified as critical and noncritical. Notifications for critical and noncriticalevents are sent in separate batches. However, a noncritical event is sent along with the critical events if thenoncritical event is pending and there is a request to read the critical events.

Critical events are related to the reachability (reachable and unreachable), connectivity (connected andunconnected), and locality (local and nonlocal) of the next hops. Notifications for these events are notdelayed.

Noncritical events include only the IGPmetric changes. These events are sent at an interval of 3 seconds.A metric change event is batched and sent 3 seconds after the last one was sent.

The next-hop trigger delay for critical and noncritical events can be configured to specify a minimum batchinginterval for critical and noncritical events using the nexthop trigger-delay command. The trigger delay isaddress family dependent.

The BGP next-hop tracking feature allows you to specify that BGP routes are resolved using only next hopswhose routes have the following characteristics:

To avoid the aggregate routes, the prefix length must be greater than a specified value.

The source protocol must be from a selected list, ensuring that BGP routes are not used to resolve nexthops that could lead to oscillation.

This route policy filtering is possible because RIB identifies the source protocol of route that resolved a nexthop as well as the mask length associated with the route. The nexthop route-policy command is used tospecify the route-policy.

For information on route policy filtering for next hops using the next-hop attach point, see the ImplementingRouting Policy Language on Cisco ASR 9000 Series Router module of Cisco ASR 9000 SeriesAggregation Services Router Routing Configuration Guide (this publication).


Implementing BGPBGP Next Hop Tracking

Scoped IPv4/VPNv4 Table WalkTo determine which address family to process, a next-hop notification is received by first de-referencing thegateway context associated with the next hop, then looking into the gateway context to determine whichaddress families are using the gateway context. The IPv4 unicast and VPNv4 unicast address families sharethe same gateway context, because they are registered with the IPv4 unicast table in the RIB. As a result, boththe global IPv4 unicast table and the VPNv4 table are is processed when an IPv4 unicast next-hop notificationis received from the RIB. A mask is maintained in the next hop, indicating if whether the next hop belongsto IPv4 unicast or VPNv4 unicast, or both. This scoped table walk localizes the processing in the appropriateaddress family table.

Reordered Address Family ProcessingThe Cisco IOS XR software walks address family tables based on the numeric value of the address family.When a next-hop notification batch is received, the order of address family processing is reordered to thefollowing order:

IPv4 tunnel

VPNv4 unicast

IPv4 labeled unicast

IPv4 unicast

IPv4 multicast

IPv6 unicast

New Thread for Next-Hop ProcessingThe critical-event thread in the spkr process handles only next-hop, Bidirectional Forwarding Detection (BFD),and fast-external-failover (FEF) notifications. This critical-event thread ensures that BGP convergence is notadversely impacted by other events that may take a significant amount of time.

show, clear, and debug CommandsThe show bgp nexthops command provides statistical information about next-hop notifications, the amountof time spent in processing those notifications, and details about each next hop registered with the RIB. Theclear bgp nexthop performance-statistics command ensures that the cumulative statistics associated withthe processing part of the next-hop show command can be cleared to help in monitoring. The clear bgpnexthop registration command performs an asynchronous registration of the next hop with the RIB. See theBGP Commands on Cisco ASR 9000 Series Router module of Routing Command Reference for Cisco ASR9000 Series Routersfor information on the next-hop show and clear commands.

The debug bgp nexthop command displays information on next-hop processing. The out keyword providesdebug information only about BGP registration of next hops with RIB. The in keyword displays debuginformation about next-hop notifications received from RIB. The out keyword displays debug informationabout next-hop notifications sent to the RIB. See the BGP Debug Commands on Cisco ASR 9000 SeriesAggregation Services Router module of Cisco ASR 9000 Series Aggregation Services Router Routing DebugCommand Reference.


Implementing BGPScoped IPv4/VPNv4 Table Walk

Autonomous System Number Formats in BGPAutonomous system numbers (ASNs) are globally unique identifiers used to identify autonomous systems(ASs) and enable ASs to exchange exterior routing information between neighboring ASs. A unique ASN isallocated to each AS for use in BGP routing. ASNs are encoded as 2-byte numbers and 4-byte numbers inBGP.

2-byte Autonomous System Number FormatThe 2-byte ASNs are represented in asplain notation. The 2-byte range is 1 to 65535.

4-byte Autonomous System Number FormatTo prepare for the eventual exhaustion of 2-byte Autonomous SystemNumbers (ASNs), BGP has the capabilityto support 4-byte ASNs. The 4-byte ASNs are represented both in asplain and asdot notations.

The byte range for 4-byte ASNs in asplain notation is 1-4294967295. The AS is represented as a 4-bytedecimal number. The 4-byte ASN asplain representation is defined in draft-ietf-idr-as-representation-01.txt.

For 4-byte ASNs in asdot format, the 4-byte range is 1.0 to 65535.65535 and the format is:

high-order-16-bit-value-in-decimal . low-order-16-bit-value-in-decimal

The BGP 4-byte ASN capability is used to propagate 4-byte-based AS path information across BGP speakersthat do not support 4-byte AS numbers. See draft-ietf-idr-as4bytes-12.txt for information on increasing thesize of an ASN from 2 bytes to 4 bytes. AS is represented as a 4-byte decimal number

as-format CommandThe as-format command configures the ASN notation to asdot. The default value, if the as-format commandis not configured, is asplain.

BGP ConfigurationBGP in Cisco IOS XR software follows a neighbor-based configuration model that requires that allconfigurations for a particular neighbor be grouped in one place under the neighbor configuration. Peer groupsare not supported for either sharing configuration between neighbors or for sharing update messages. Theconcept of peer group has been replaced by a set of configuration groups to be used as templates in BGPconfiguration and automatically generated update groups to share update messages between neighbors.

Configuration ModesBGP configurations are grouped into modes. The following sections show how to enter some of the BGPconfiguration modes. From a mode, you can enter the ? command to display the commands available in thatmode.

Router Configuration Mode

The following example shows how to enter router configuration mode:

RP/0/RSP0/CPU0:router# configurationRP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)#


Implementing BGPAutonomous System Number Formats in BGP

https://tools.ietf.org/html/draft-ietf-idr-as-representation-01https://tools.ietf.org/html/draft-ietf-idr-as4bytes-12

Router Address Family Configuration Mode

The following example shows how to enter router address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 112RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-af)#

Neighbor Configuration Mode

The following example shows how to enter neighbor configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.0.1RP/0/RSP0/CPU0:router(config-bgp-nbr)#

Neighbor Address Family Configuration Mode

The following example shows how to enter neighbor address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 112RP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.0.0.1RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-nbr-af)#

VRF Configuration Mode

The following example shows how to enter VPN routing and forwarding (VRF) configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_ARP/0/RSP0/CPU0:router(config-bgp-vrf)#

VRF Address Family Configuration Mode

The following example shows how to enter VRF address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 112RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_ARP/0/RSP0/CPU0:router(config-bgp-vrf)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-vrf-af)#

Configuring Resilient Per-CE Label Mode Under VRF Address Family

Perform this task to configure resilient per-ce label mode under VRF address family.

Resilient per-CE 6PE label allocation is not supported on CRS-1 and CRS-3 routers, but supported only onASR 9000 routers.

Note


Implementing BGPRouter Address Family Configuration Mode

SUMMARY STEPS

1. configure2. router bgpas-number3. vrfvrf-instance4. address-family {ipv4 | ipv6} unicast5. label mode per-ce6. Do one of the following:

end commit

DETAILED STEPS

Step 1 configure

Example:

RP/0/RSP0/CPU0:router# configureRP/0/RSP0/CPU0:router(config)#

Enters global configuration mode.

Step 2 router bgpas-number

Example:

RP/0/RSP0/CPU0:router(config)# router bgp 666RP/0/RSP0/CPU0:router(config-bgp)#

Specifies the autonomous system number and enters the BGP configuration mode, allowing you to configure the BGProuting process.

Step 3 vrfvrf-instance

Example:

RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf-peRP/0/RSP0/CPU0:router(config-bgp-vrf)#

Configures a VRF instance.

Step 4 address-family {ipv4 | ipv6} unicast

Example:

RP/0/RSP0/CPU0:router(config-bgp-vrf)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-vrf-af)#

Specifies either an IPv4 or IPv6 address family unicast and enters address family configuration submode.

Step 5 label mode per-ce

Example:


Implementing BGPConfiguring Resilient Per-CE Label Mode Under VRF Address Family

RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# label mode per-ceRP/0/RSP0/CPU0:router(config-bgp-vrf-af)#

Configures resilient per-ce label mode.

Step 6 Do one of the following:

end commit

Example:

RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# end

or

RP/0/RSP0/CPU0:router(config-bgp-vrf-af)# commit

Saves configuration changes.

When you issue the end command, the system prompts you to commit changes:

Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:

Entering yes saves configuration changes to the running configuration file, exits the configuration session, andreturns the router to EXEC mode.

Entering no exits the configuration session and returns the router to EXEC mode without committing theconfiguration changes.

Entering cancel leaves the router in the current configuration session without exiting or committing theconfiguration changes.

Use the commit command to save the configuration changes to the running configuration file and remain within theconfiguration session.

Configuring Resilient Per-CE Label Mode Using a Route-Policy

Perform this task to configure resilient per-ce label mode using a route-policy.

Resilient per-CE 6PE label allocation is not supported on CRS-1 and CRS-3 routers, but supported only onASR 9000 routers.

Note

SUMMARY STEPS

1. configure2. route-policypolicy-name3. set label mode per-ce4. Do one of the following:

end


Implementing BGPConfiguring Resilient Per-CE Label Mode Using a Route-Policy

commit

DETAILED STEPS

Step 1 configure

Example:

RP/0/RSP0/CPU0:router# configureRP/0/RSP0/CPU0:router(config)#

Enters global configuration mode.

Step 2 route-policypolicy-name

Example:

RP/0/RSP0/CPU0:router(config)# route-policy route1RP/0/RSP0/CPU0:router(config-rpl)#

Creates a route policy and enters route policy configuration mode.

Step 3 set label mode per-ce

Example:

RP/0/RSP0/CPU0:router(config-rpl)# set label mode per-ceRP/0/RSP0/CPU0:router(config-rpl)#

Configures resilient per-ce label mode.

Step 4 Do one of the following:

end commit

Example:

RP/0/RSP0/CPU0:router(config-rpl)# end

or

RP/0/RSP0/CPU0:router(config-rpl)# commit

Saves configuration changes.

When you issue the end command, the system prompts you to commit changes:

Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:

Entering yes saves configuration changes to the running configuration file, exits the configuration session, andreturns the router to EXEC mode.

Entering no exits the configuration session and returns the router to EXEC mode without committing theconfiguration changes.


Implementing BGPConfiguring Resilient Per-CE Label Mode Using a Route-Policy

Entering cancel leaves the router in the current configuration session without exiting or committing theconfiguration changes.

Use the commit command to save the configuration changes to the running configuration file and remain within theconfiguration session.

VRF Neighbor Configuration Mode

The following example shows how to enter VRF neighbor configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_ARP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)#

VRF Neighbor Address Family Configuration Mode

The following example shows how to enter VRF neighbor address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 112RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_ARP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)#

VPNv4 Address Family Configuration Mode

The following example shows how to enter VPNv4 address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 152RP/0/RSP0/CPU0:router(config-bgp)# address-family vpnv4 unicastRP/0/RSP0/CPU0:router(config-bgp-af)#

L2VPN Address Family Configuration Mode

The following example shows how to enter L2VPN address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 100RP/0/RSP0/CPU0:router(config-bgp)# address-family l2vpn vpls-vpwsRP/0/RSP0/CPU0:router(config-bgp-af)#

Neighbor SubmodeCisco IOS XR BGP uses a neighbor submode to make it possible to enter configurations without having toprefix every configuration with the neighbor keyword and the neighbor address:

Cisco IOS XR software has a submode available for neighbors in which it is not necessary for everycommand to have a neighbor x.x.x.x prefix:

In Cisco IOS XR software, the configuration is as follows:


Implementing BGPVRF Neighbor Configuration Mode

RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.23.1.2RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2002RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicast

An address family configuration submode inside the neighbor configuration submode is available forentering address family-specific neighbor configurations. In Cisco IOS XR software, the configurationis as follows:

RP/0/RSP0/CPU0:router(config-bgp)# neighbor 2002::2RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 2023RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv6 unicastRP/0/RSP0/CPU0:router(config-bgp-nbr-af)# next-hop-selfRP/0/RSP0/CPU0:router(config-bgp-nbr-af)# route-policy one in

You must enter neighbor-specific IPv4, IPv6, VPNv4, or VPNv6 commands in neighbor address-familyconfiguration submode. In Cisco IOS XR software, the configuration is as follows:

RP/0/RSP0/CPU0:router(config)# router bgp 109RP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.40.24RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1RP/0/RSP0/CPU0:router(config-bgp-nbr)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-nbr-af)# maximum-prefix 1000

Youmust enter neighbor-specific IPv4 and IPv6 commands in VRF neighbor address-family configurationsubmode. In Cisco IOS XR software, the configuration is as follows:

RP/0/RSP0/CPU0:router(config)# router bgp 110RP/0/RSP0/CPU0:router(config-bgp)# vrf vrf_ARP/0/RSP0/CPU0:router(config-bgp-vrf)# neighbor 11.0.1.2RP/0/RSP0/CPU0:router(config-bgp-vrf-nbr)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-vrf-nbr-af)# route-policy pass all in

Configuration TemplatesThe af-group, session-group, and neighbor-group configuration commands provide template support forthe neighbor configuration in Cisco IOS XR software.

The af-group command is used to group address family-specific neighbor commands within an IPv4, IPv6,or VPNv4, address family. Neighbors that have the same address family configuration are able to use theaddress family group (af-group) name for their address family-specific configuration. A neighbor inherits theconfiguration from an address family group by way of the use command. If a neighbor is configured to usean address family group, the neighbor (by default) inherits the entire configuration from the address familygroup. However, a neighbor does not inherit all of the configuration from the address family group if itemsare explicitly configured for the neighbor. The address family group configuration is entered under the BGProuter configuration mode. The following example shows how to enter address family group configurationmode.

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# af-group afmcast1 address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-afgrp)#


Implementing BGPConfiguration Templates

The session-group command allows you to create a session group from which neighbors can inherit addressfamily-independent configuration. A neighbor inherits the configuration from a session group by way of theuse command. If a neighbor is configured to use a session group, the neighbor (by default) inherits the entireconfiguration of the session group. A neighbor does not inherit all of the configuration from a session groupif a configuration is done directly on that neighbor. The following example shows how to enter session groupconfiguration mode:

RP/0/RSP0/CPU0:router# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# session-group session1RP/0/RSP0/CPU0:router(config-bgp-sngrp)#

The neighbor-group command helps you apply the same configuration to one or more neighbors. Neighborgroups can include session groups and address family groups and can comprise the complete configurationfor a neighbor. After a neighbor group is configured, a neighbor can inherit the configuration of the groupusing the use command. If a neighbor is configured to use a neighbor group, the neighbor inherits the entireBGP configuration of the neighbor group.

The following example shows how to enter neighbor group configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 123RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)#

The following example shows how to enter neighbor group address family configuration mode:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group nbrgroup1RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# address-family ipv4 unicastRP/0/RSP0/CPU0:router(config-bgp-nbrgrp-af)#

However, a neighbor does not inherit all of the configuration from the neighbor group if items areexplicitly configured for the neighbor. In addition, some part of the configuration of the neighbor groupcould be hidden if a session group or address family group was also being used.

Configuration grouping has the following effects in Cisco IOS XR software:

Commands entered at the session group level define address family-independent commands (the samecommands as in the neighbor submode).

Commands entered at the address family group level define address family-dependent commands for aspecified address family (the same commands as in the neighbor-address family configuration submode).

Commands entered at the neighbor group level define address family-independent commands and addressfamily-dependent commands for each address family (the same as all available neighbor commands),and define the use command for the address family group and session group commands.

Template Inheritance RulesIn Cisco IOS XR software, BGP neighbors or groups inherit configuration from other configuration groups.

For address family-independent configurations:

Neighbors can inherit from session groups and neighbor groups.


Implementing BGPTemplate Inheritance Rules

Neighbor groups can inherit from session groups and other neighbor groups.

Session groups can inherit from other session groups.

If a neighbor uses a session group and a neighbor group, the configurations in the session group arepreferred over the global address family configurations in the neighbor group.

For address family-dependent configurations:

Address family groups can inherit from other address family groups.

Neighbor groups can inherit from address family groups and other neighbor groups.

Neighbors can inherit from address family groups and neighbor groups.

Configuration group inheritance rules are numbered in order of precedence as follows:

1. If the item is configured directly on the neighbor, that value is used. In the example that follows, theadvertisement interval is configured both on the neighbor group and neighbor configuration and theadvertisement interval being used is from the neighbor configuration:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 15RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exitRP/0/RSP0/CPU0:router(config-bgp)# neighbor 10.1.1.1RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1RP/0/RSP0/CPU0:router(config-bgp-nbr)# advertisement-interval 20

The following output from the show bgp neighbors command shows that the advertisement interval usedis 20 seconds:

RP/0/RSP0/CPU0:router# show bgp neighbors 10.1.1.1

BGP neighbor is 10.1.1.1, remote AS 1, local AS 140, external linkRemote router ID 0.0.0.0BGP state = IdleLast read 00:00:00, hold time is 180, keepalive interval is 60 secondsReceived 0 messages, 0 notifications, 0 in queueSent 0 messages, 0 notifications, 0 in queueMinimum time between advertisement runs is 20 seconds

For Address Family: IPv4 UnicastBGP neighbor version 0Update group: 0.1eBGP neighbor with no inbound or outbound policy; defaults to 'drop'Route refresh request: received 0, sent 00 accepted prefixesPrefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288Threshold for warning message 75%

Connections established 0; dropped 0Last reset 00:00:14, due to BGP neighbor initializedExternal BGP neighbor not directly connected.

2. Otherwise, if an item is configured to be inherited from a session-group or neighbor-group and on theneighbor directly, then the configuration on the neighbor is used. If a neighbor is configured to be inherited


Implementing BGPTemplate Inheritance Rules

from session-group or af-group, but no directly configured value, then the value in the session-group oraf-group is used. In the example that follows, the advertisement interval is configured on a neighbor groupand a session group and the advertisement interval value being used is from the session group:

RP/0/RSP0/CPU0:router(config)# router bgp 140RP/0/RSP0/CPU0:router(config-bgp)# session-group AS_2RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 15RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exitRP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# advertisement-interval 20RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exitRP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.0.1RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1RP/0/RSP0/CPU0:router(config-bgp-nbr)# use session-group AS_2RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1

The following output from the show bgp neighbors command shows that the advertisement interval usedis 15 seconds:

RP/0/RSP0/CPU0:router# show bgp neighbors 192.168.0.1

BGP neighbor is 192.168.0.1, remote AS 1, local AS 140, external linkRemote router ID 0.0.0.0BGP state = IdleLast read 00:00:00, hold time is 180, keepalive interval is 60 secondsReceived 0 messages, 0 notifications, 0 in queueSent 0 messages, 0 notifications, 0 in queueMinimum time between advertisement runs is 15 seconds

For Address Family: IPv4 UnicastBGP neighbor version 0Update group: 0.1eBGP neighbor with no inbound or outbound policy; defaults to 'drop'Route refresh request: received 0, sent 00 accepted prefixesPrefix advertised 0, suppressed 0, withdrawn 0, maximum limit 524288Threshold for warning message 75%

Connections established 0; dropped 0Last reset 00:03:23, due to BGP neighbor initializedExternal BGP neighbor not directly connected.

3. Otherwise, if the neighbor uses a neighbor group and does not use a session group or address family group,the configuration value can be obtained from the neighbor group either directly or through inheritance.In the example that follows, the advertisement interval from the neighbor group is used because it is notconfigured directly on the neighbor and no session group is used:

RP/0/RSP0/CPU0:router(config)# router bgp 150RP/0/RSP0/CPU0:router(config-bgp)# session-group AS_2RP/0/RSP0/CPU0:router(config-bgp-sngrp)# advertisement-interval 20RP/0/RSP0/CPU0:router(config-bgp-sngrp)# exitRP/0/RSP0/CPU0:router(config-bgp)# neighbor-group AS_1RP/0/RSP0/CPU0:router(con

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