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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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xiii
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xiv
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xv
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xvi
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xvii
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xviii
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xix
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xx
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxi
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxii
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxiii
Contents
BFD over MPLS TE Tunnel Head-end Configuration: Example 339
BFD over MPLS TE Tunnel Tail-end Configuration: Example 339
Where to Go Next 339
Additional References 340
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxiv
Contents
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
Additional References 378
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxv
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxvi
Contents
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxvii
Contents
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
Where to Go Next 444
Additional References 444
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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.xxviii
Contents
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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Contents
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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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
Where to Go Next 545
Additional References 546
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
Additional References 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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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
Where to Go Next 570
Additional References 571
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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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
Additional References 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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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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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
Additional References 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
Additional References 698
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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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
Additional References 744
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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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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.
Release 6.5.1This feature wasintroduced.
IS-IS Distribute List
See Purge OriginatorIdentification TLV forIS-IS section inImplementing IS-ISchapter.
Release 6.5.1This feature wasintroduced.
Purge OriginatorIdentification TLV forIS-IS
ConfiguringAuthenticationMessage DigestManagement forOSPF, on page 526
Release 6.5.1This feature wasintroduced.
OSPFAuthenticationwithKeychain
Implementing IS-ISchapter.
Release 6.5.1This feature wasintroduced.
Configuring GlobalWeighted SRLGProtection
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Where DocumentedChanged in ReleaseDescriptionFeature
See
BGP SessionAuthentication andIntegrity using TCPAuthentication andOption Overview
section
in Implementing BGPchapter
Release 6.5.1This feature wasintroduced.
BGP SessionAuthentication andIntegrity using TCPAuthentication Option
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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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.5.x3
ModificationRelease
The following features were supported:
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
The following features were supported:
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
The following features were supported:
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
The following features were supported:
Per-neighbor Link Bandwidth
Release 4.3.2
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Implementing BGP
ModificationRelease
The following features were supported:
L3VPN iBGP-PE-CE configuration
Source-based flow tag
Discard extra paths
Release 5.3.1
The following features were supported:
Graceful Maintenance
Per Neighbor TCP MSS
BGP DMZ Aggregate Bandwidth
Release 5.3.2
The following features were supported:
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.
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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
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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
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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).
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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).
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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.
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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)#
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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
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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:
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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
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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.
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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:
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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)#
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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.
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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
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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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