Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOSXR Release 6.3.xFirst Published: 2017-09-15
Last Modified: 2018-03-01
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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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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
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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
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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
L3VPN iBGP PE-CE 156
L3VPN iBGP PE-CE Overview 156
Restrictions for L3VPN iBGP PE-CE 157
Configuring L3VPN iBGP PE-CE 157
Flow-tag propagation 160
Restrictions for flow-tag propagation 160
Source and destination-based flow tag 160
Configure Source and Destination-based Flow Tag 160
Configuring a VPN Routing and Forwarding Instance in BGP 162
Defining Virtual Routing and Forwarding Tables in Provider Edge Routers 162
Configuring the Route Distinguisher 164
Configuring PE-PE or PE-RR Interior BGP Sessions 165
Configuring Route Reflector to Hold Routes That Have a Defined Set of RT Communities 168
Configuring BGP as a PE-CE Protocol 169
Redistribution of IGPs to BGP 172
Configuring Keychains for BGP 174
Disabling a BGP Neighbor 175
Neighbor Capability Suppression 176
Configuration: 176
BGP Dynamic Neighbors 176
Configuring BGP Dynamic Neighbors using Address Range 177
Remote AS 178
Maximum-peers and Idle-watch timeout 180
Resetting Neighbors Using BGP Inbound Soft Reset 181
Resetting Neighbors Using BGP Outbound Soft Reset 182
Resetting Neighbors Using BGP Hard Reset 182
Clearing Caches, Tables, and Databases 183
Displaying System and Network Statistics 184
Displaying BGP Process Information 186
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Monitoring BGP Update Groups 187
Configuring BGP Nonstop Routing 188
Disable BGP Nonstop Routing 188
Re-enable BGP Nonstop Routing 188
Installing Primary Backup Path for Prefix Independent Convergence (PIC) 189
Retaining Allocated Local Label for Primary Path 190
Configuring BGP Additional Paths 191
Configuring iBGP Multipath Load Sharing 193
Originating Prefixes with AiGP 193
Configuring BGP Accept Own 195
Configuring BGP Link-State 196
Configuring BGP Link-state 196
Configuring Domain Distinguisher 197
Configuring BGP Permanent Network 197
Configuring BGP Permanent Network 197
How to Advertise Permanent Network 199
Enabling BGP Unequal Cost Recursive Load Balancing 200
Configuring VRF Dynamic Route Leaking 202
Enabling Selective VRF Download 203
Disabling Selective VRF Download 205
Configuring Resilient Per-CE Label Mode 207
Configuring Resilient Per-CE Label Mode Under VRF Address Family 207
Configuring Resilient Per-CE Label Mode Using a Route-Policy 209
Configuring BGP Large Communities 210
Configuration Examples for Implementing BGP 215
Enabling BGP: Example 215
Displaying BGP Update Groups: Example 217
BGP Neighbor Configuration: Example 217
BGP Confederation: Example 218
BGP Route Reflector: Example 220
BGP Nonstop Routing Configuration: Example 220
Primary Backup Path Installation: Example 220
Allocated Local Label Retention: Example 220
iBGP Multipath Loadsharing Configuration: Example 221
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Contents
Discard Extra Paths Configuration: Example 221
Displaying Discard Extra Paths Information: Example 221
Configure Per Neighbor TCP MSS: Examples 222
Verify Per Neighbor TCP MSS: Examples 224
Originating Prefixes With AiGP: Example 226
BGP Accept Own Configuration: Example 226
BGP Unequal Cost Recursive Load Balancing: Example 227
VRF Dynamic Route Leaking Configuration: Example 229
Resilient Per-CE Label Mode Configuration: Example 230
Configuring Resilient Per-CE Label Mode Under VRF Address Family: Example 230
Configuring Resilient Per-CE Label Mode Using a Route-Policy: Example 230
Flow-tag propagation 230
Restrictions for Flow-Tag Propagation 231
Where to Go Next 231
Additional References 231
Implementing BGP Flowspec 235C H A P T E R 3
BGP Flow Specification 235
Limitations 236
BGP Flowspec Conceptual Architecture 236
Information About Implementing BGP Flowspec 237
Flow Specifications 237
Supported Matching Criteria and Actions 238
Traffic Filtering Actions 242
BGP Flowspec Client-Server (Controller) Model and Configuration with ePBR 243
Configuring BGP Flowspec with ePBR 244
Enable BGP Flowspec 245
Configure a Class Map 246
Configure a Policy Map 248
Link BGP Flowspec to ePBR Policies 249
Verify BGP Flowspec 253
Preserving Redirect Nexthop 255
Validate BGP Flowspec 256
Disabling BGP Flowspec 257
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Disable Flowspec Redirect and Validation 258
Configuration Examples for Implementing BGP Flowspec 259
Flowspec Rule Configuration 259
Drop Packet Length 260
Redirect traffic and rate-limit: Example 260
Redirect Traffic from Global to VRF (vrf1) 261
Remark DSCP 261
Additional References for BGP Flowspec 261
Implementing BFD 263C H A P T E R 4
Prerequisites for Implementing BFD 265
Restrictions for Implementing BFD 266
Information About BFD 267
Differences in BFD in Cisco IOS XR Software and Cisco IOS Software 267
BFD Multipath Sessions Support on nV Edge System 268
BFD Modes of Operation 268
BFD Packet Information 269
BFD Source and Destination Ports 269
BFD Packet Intervals and Failure Detection 269
Priority Settings for BFD Packets 273
BFD for IPv4 274
BFD for IPv6 275
BFD on Bundled VLANs 275
BFD Over Member Links on Link Bundles 276
Overview of BFD State Change Behavior on Member Links and Bundle Status 277
BFD Multipath Sessions 278
BFD for MultiHop Paths 279
Setting up BFD Multihop 279
BFD over MPLS Traffic Engineering LSPs 279
Echo Timer configuration for BFD on Bundle Interfaces 280
Bidirectional Forwarding Detection over Logical Bundle 281
Bidirectional Forwarding Detection over Generic Routing Encapsulation 281
Configure Bidirectional Forwarding Detection over Generic Routing Encapsulation 282
Bidirectional Forwarding Detection IPv6 Multihop 285
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BFD over Pseudowire Headend 285
BFD over Satellite Interfaces 285
BFD over IRB 286
BFD over Bundle Per-Member Link 286
BFD over Bundles CISCO/IETF Mode Support on a Per Bundle Basis 287
BFD Dampening 288
BFD Hardware Offload 288
BFD Object Tracking 289
How to Configure BFD 290
BFD Configuration Guidelines 290
Configuring BFD Under a Dynamic Routing Protocol or Using a Static Route 290
Enabling BFD on a BGP Neighbor 290
Enabling BFD for OSPF on an Interface 292
Enabling BFD for OSPFv3 on an Interface 294
Enabling BFD on a Static Route 295
Enabling BFD on a IPv6 Static Route 296
Configuring BFD on Bundle Member Links 297
Prerequisites for Configuring BFD on Bundle Member Links 297
Specifying the BFD Destination Address on a Bundle 297
Enabling BFD Sessions on Bundle Members 297
Configuring the Minimum Thresholds for Maintaining an Active Bundle 298
Configuring BFD Packet Transmission Intervals and Failure Detection Times on a Bundle 299
Configuring Allowable Delays for BFD State Change Notifications Using Timers on a Bundle300
Configure BFD over Bundles CISCO/IETF Mode Support on a Per Bundle Basis 301
Configuring BFD over Bundle for Hardware Offload 303
Enabling Echo Mode to Test the Forwarding Path to a BFD Peer 306
Overriding the Default Echo Packet Source Address 306
Specifying the Echo Packet Source Address Globally for BFD 307
Specifying the Echo Packet Source Address on an Individual Interface or Bundle 307
Configuring BFD Session Teardown Based on Echo Latency Detection 308
Delaying BFD Session Startup Until Verification of Echo Path and Latency 309
Disabling Echo Mode 310
Disabling Echo Mode on a Router 310
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Contents
Disabling Echo Mode on an Individual Interface or Bundle 311
Minimizing BFD Session Flapping Using BFD Dampening 312
Enabling and Disabling IPv6 Checksum Support 312
Enabling and Disabling IPv6 Checksum Calculations for BFD on a Router 313
Enabling and Disabling IPv6 Checksum Calculations for BFD on an Individual Interface orBundle 313
Clearing and Displaying BFD Counters 314
Configuring Coexistence Between BFD over Bundle (BoB) and BFD over Logical Bundle (BLB)315
BFD IPv6 in Bundle Manager Domain 316
Configuration: 316
Configuring BFD IPv6 Multihop 318
Configuring BFD IPv6 Multihop for eBGP Neighbors 318
Configuring BFD IPv6 Multihop for iBGP Neighbors 318
Configuring BFD over MPLS Traffic Engineering LSPs 319
Enabling BFD Parameters for BFD over TE Tunnels 319
Configuring BFD Bring up Timeout 320
Configuring BFD Dampening for TE Tunnels 321
Configuring Periodic LSP Ping Requests 322
Configuring BFD at the Tail End 323
Configuring BFD over LSP Sessions on Line Cards 324
Configuring BFD Object Tracking: 325
Configuration Examples for Configuring BFD 326
BFD Over BGP: Example 326
BFD Over OSPF: Examples 326
BFD Over Static Routes: Examples 327
BFD on Bundled VLANs: Example 327
BFD Over Bridge Group Virtual Interface: Example 328
BFD on Bundle Member Links: Examples 330
Echo Packet Source Address: Examples 331
Echo Latency Detection: Examples 332
Echo Startup Validation: Examples 332
BFD Echo Mode Disable: Examples 333
BFD Dampening: Examples 333
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Contents
BFD IPv6 Checksum: Examples 333
BFD Peers on Routers Running Cisco IOS and Cisco IOS XR Software: Example 334
BFD Over Bundle Hardware Offload: Example 334
Configuring BFD IPv6 Multihop: Examples 336
BFD over MPLS TE LSPs: Examples 336
BFD over MPLS TE Tunnel Head-end Configuration: Example 336
BFD over MPLS TE Tunnel Tail-end Configuration: Example 336
Where to Go Next 337
Additional References 337
Related Documents 337
Standards 337
RFCs 338
MIBs 338
Technical Assistance 338
Implementing EIGRP 339C H A P T E R 5
Prerequisites for Implementing EIGRP 340
Restrictions for Implementing EIGRP 340
Information About Implementing EIGRP 340
EIGRP Functional Overview 340
EIGRP Features 341
EIGRP Components 341
EIGRP Configuration Grouping 342
EIGRP Configuration Modes 342
EIGRP Interfaces 343
Redistribution for an EIGRP Process 343
Metric Weights for EIGRP Routing 344
Mismatched K Values 344
Goodbye Message 345
Percentage of Link Bandwidth Used for EIGRP Packets 345
Floating Summary Routes for an EIGRP Process 345
Split Horizon for an EIGRP Process 347
Adjustment of Hello Interval and Hold Time for an EIGRP Process 347
Stub Routing for an EIGRP Process 348
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Contents
Route Policy Options for an EIGRP Process 349
EIGRP Layer 3 VPN PE-CE Site-of-Origin 350
Router Interoperation with the Site-of-Origin Extended Community 350
Route Manipulation using SoO match condition 350
EIGRP v4/v6 Authentication Using Keychain 352
EIGRP Wide Metric Computation 352
EIGRP Multi-Instance 353
EIGRP Support for BFD 353
How to Implement EIGRP 353
Enabling EIGRP Routing 353
Configuring Route Summarization for an EIGRP Process 355
Redistributing Routes for EIGRP 356
Creating a Route Policy and Attaching It to an EIGRP Process 358
Configuring Stub Routing for an EIGRP Process 359
Configuring EIGRP as a PE-CE Protocol 360
Redistributing BGP Routes into EIGRP 362
Monitoring EIGRP Routing 363
Configuring an EIGRP Authentication Keychain 366
Configuring an Authentication Keychain for an IPv4/IPv6 Interface on a Default VRF 366
Configuring an Authentication Keychain for an IPv4/IPv6 Interface on a Nondefault VRF 367
Configuring unicast neighbors 368
Remote Neighbor Session Policy 368
Understanding Neighbor Terms 369
Remote Unicast-Listen (Point-to-Point) Neighbors 370
Restrictions for remote neighbors 370
Inheritance and precedence of the remote neighbor configurations 370
How to configure remote unicast neighbors 371
Configuration Examples for Implementing EIGRP 372
Configuring a Basic EIGRP Configuration: Example 372
Configuring an EIGRP Stub Operation: Example 373
Configuring an EIGRP PE-CE Configuration with Prefix-Limits: Example 373
Configuring an EIGRP Authentication Keychain: Example 373
Additional References 374
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Contents
Implementing IS-IS 377C H A P T E R 6
Prerequisites for Implementing IS-IS 377
Restrictions for Implementing IS-IS 377
Information About Implementing IS-IS 378
IS-IS Functional Overview 378
Key Features Supported in the Cisco IOS XR IS-IS Implementation 378
IS-IS Configuration Grouping 379
IS-IS Configuration Modes 379
Router Configuration Mode 379
Router Address Family Configuration Mode 379
Interface Configuration Mode 379
Interface Address Family Configuration Mode 379
IS-IS Interfaces 380
Multitopology Configuration 380
IPv6 Routing and Configuring IPv6 Addressing 380
Limit LSP Flooding 380
Flood Blocking on Specific Interfaces 381
Mesh Group Configuration 381
Maximum LSP Lifetime and Refresh Interval 381
Single-Topology IPv6 Support 381
Multitopology IPv6 for IS-IS 382
IS-IS Authentication 382
Nonstop Forwarding 383
ISIS NSR 384
Configuring IS-IS Adjacency Stagger 384
Multi-Instance IS-IS 385
Multiprotocol Label Switching Traffic Engineering 385
Overload Bit on Router 385
Overload Bit Configuration During Multitopology Operation 386
IS-IS Overload Bit Avoidance 386
Default Routes 386
Attached Bit on an IS-IS Instance 386
IS-IS Support for Route Tags 387
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Contents
Multicast-Intact Feature 387
Multicast Topology Support Using IS-IS 387
MPLS Label Distribution Protocol IGP Synchronization 388
MPLS LDP-IGP Synchronization Compatibility with LDP Graceful Restart 388
MPLS LDP-IGP Synchronization Compatibility with IGP Nonstop Forwarding 388
Label Distribution Protocol IGP Auto-configuration 388
MPLS TE Forwarding Adjacency 389
MPLS TE Interarea Tunnels 389
IP Fast Reroute 389
Unequal Cost Multipath Load-balancing for IS-IS 389
Enabling IS-IS and Configuring Level 1 or Level 2 Routing 390
Configuring Single Topology for IS-IS 392
Configuring Multitopology Routing 396
Restrictions for Configuring Multitopology Routing 396
Information About Multitopology Routing 396
Configuring a Global Topology and Associating It with an Interface 396
Enabling an IS-IS Topology 398
Placing an Interface in a Topology in IS-IS 398
Configuring a Routing Policy 399
Configuring Multitopology for IS-IS 400
Controlling LSP Flooding for IS-IS 400
Configuring Nonstop Forwarding for IS-IS 404
Configuring ISIS-NSR 405
Configuring Authentication for IS-IS 407
Configuring Keychains for IS-IS 409
Configuring MPLS Traffic Engineering for IS-IS 410
Tuning Adjacencies for IS-IS 412
Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration 414
Customizing Routes for IS-IS 416
Configuring MPLS LDP IS-IS Synchronization 418
Enabling Multicast-Intact 419
Tagging IS-IS Interface Routes 420
Setting the Priority for Adding Prefixes to the RIB 422
Configuring IP Fast Reroute Loop-free Alternate 422
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Contents
Configuring IS-IS Overload Bit Avoidance 424
ISIS Link Group 425
Configure Link Group Profile 425
Configure Link Group Interface 427
Configuration Examples for Implementing IS-IS 429
Configuring Single-Topology IS-IS for IPv6: Example 429
Configuring Multitopology IS-IS for IPv6: Example 429
Redistributing IS-IS Routes Between Multiple Instances: Example 430
Tagging Routes: Example 430
Configuring IS-IS Overload Bit Avoidance: Example 431
Example: Configuring IS-IS To Handle Router Overload 431
Where to Go Next 436
Additional References 436
Implementing OSPF 439C H A P T E R 7
Prerequisites for Implementing OSPF 440
Information About Implementing OSPF 441
OSPF Functional Overview 441
Key Features Supported in the Cisco IOS XR Software OSPF Implementation 442
Comparison of Cisco IOS XR Software OSPFv3 and OSPFv2 443
OSPF Hierarchical CLI and CLI Inheritance 443
OSPF Routing Components 444
Autonomous Systems 444
Areas 444
Routers 445
OSPF Process and Router ID 446
Supported OSPF Network Types 447
Route Authentication Methods for OSPF 447
Plain Text Authentication 447
MD5 Authentication 447
Authentication Strategies 447
Key Rollover 448
Neighbors and Adjacency for OSPF 448
OSPF strict-mode Support for BFD Dampening 448
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Contents
Enabling strict-mode 448
BFD strict-mode: Example 449
OSPF FIB Download Notification 450
Designated Router (DR) for OSPF 451
Default Route for OSPF 451
Link-State Advertisement Types for OSPF Version 2 451
Link-State Advertisement Types for OSPFv3 452
Virtual Link and Transit Area for OSPF 453
Passive Interface 454
OSPFv2 Sham Link Support for MPLS VPN 454
OSPFv3 Sham Link Support for MPLS VPN 456
Graceful Restart Procedure over the Sham-link 456
ECMP and OSPFv3 Sham-link 457
OSPF SPF Prefix Prioritization 457
Route Redistribution for OSPF 458
OSPF Shortest Path First Throttling 458
Nonstop Forwarding for OSPF Version 2 459
Graceful Shutdown for OSPFv3 460
Modes of Graceful Restart Operation 460
Graceful Restart Requirements and Restrictions 462
Warm Standby and Nonstop Routing for OSPF Version 2 463
Warm Standby for OSPF Version 3 463
Multicast-Intact Support for OSPF 464
Load Balancing in OSPF Version 2 and OSPFv3 464
Configure Prefix Suppression for OSPF 464
Configure Prefix Suppression for OSPFv3 469
Multi-Area Adjacency for OSPF Version 2 474
Label Distribution Protocol IGP Auto-configuration for OSPF 474
OSPF Authentication Message Digest Management 475
GTSM TTL Security Mechanism for OSPF 475
Path Computation Element for OSPFv2 475
OSPF IP Fast Reroute Loop Free Alternate 476
Management Information Base (MIB) for OSPFv3 476
VRF-lite Support for OSPFv2 476
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Contents
OSPFv3 Timers Link-state Advertisements and Shortest Path First Throttle Default Values Update477
Unequal Cost Multipath Load-balancing for OSPF 477
How to Implement OSPF 478
Enabling OSPF 478
Configuring Stub and Not-So-Stubby Area Types 479
Configuring Neighbors for Nonbroadcast Networks 481
Configuring Authentication at Different Hierarchical Levels for OSPF Version 2 484
Controlling the Frequency That the Same LSA Is Originated or Accepted for OSPF 487
Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF 489
Examples 492
Summarizing Subnetwork LSAs on an OSPF ABR 492
Redistribute Routes into OSPF 494
Configuring OSPF Shortest Path First Throttling 496
Examples 498
Configuring Nonstop Forwarding Specific to Cisco for OSPF Version 2 498
Configuring OSPF Version 2 for MPLS Traffic Engineering 500
Examples 502
Configuring OSPFv3 Graceful Restart 504
Displaying Information About Graceful Restart 505
Configuring an OSPFv2 Sham Link 506
Configuring OSPF SPF Prefix Prioritization 508
Enabling Multicast-intact for OSPFv2 510
Associating Interfaces to a VRF 511
Configuring OSPF as a Provider Edge to Customer Edge (PE-CE) Protocol 512
Creating Multiple OSPF Instances (OSPF Process and a VRF) 514
Configuring Multi-area Adjacency 515
Configuring Label Distribution Protocol IGP Auto-configuration for OSPF 516
Configuring LDP IGP Synchronization: OSPF 517
Configuring Authentication Message Digest Management for OSPF 518
Examples 519
Configuring Generalized TTL Security Mechanism (GTSM) for OSPF 520
Examples 522
Verifying OSPF Configuration and Operation 523
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Contents
Configuring IP Fast Reroute Loop-free Alternate 525
Enabling IPFRR LFA 525
Excluding an Interface From IP Fast Reroute Per-link Computation 526
Enabling OSPF Interaction with SRMS Server 526
Configuration Examples for Implementing OSPF 528
Cisco IOS XR Software for OSPF Version 2 Configuration: Example 528
CLI Inheritance and Precedence for OSPF Version 2: Example 529
MPLS TE for OSPF Version 2: Example 530
ABR with Summarization for OSPFv3: Example 530
ABR Stub Area for OSPFv3: Example 531
ABR Totally Stub Area for OSPFv3: Example 531
Configuring OSPF SPF Prefix Prioritization: Example 531
Route Redistribution for OSPFv3: Example 532
Virtual Link Configured Through Area 1 for OSPFv3: Example 533
Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example 533
VPN Backbone and Sham Link Configured for OSPF Version 2: Example 534
Where to Go Next 537
Additional References 537
Implementing IP Fast Reroute Loop-Free Alternate 541C H A P T E R 8
Prerequisites for IPv4/IPv6 Loop-Free Alternate Fast Reroute 541
Restrictions for Loop-Free Alternate Fast Reroute 541
IS-IS and IP FRR 542
Repair Paths 542
LFA Overview 543
LFA Calculation 543
Interaction Between RIB and Routing Protocols 543
Configuring Fast Reroute Support 544
Configuring IPv4 Loop-Free Alternate Fast Reroute Support: Example 546
Additional References 546
Implementing and Monitoring RIB 549C H A P T E R 9
Prerequisites for Implementing RIB 550
Information About RIB Configuration 550
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Contents
Overview of RIB 550
RIB Data Structures in BGP and Other Protocols 550
RIB Administrative Distance 550
RIB Support for IPv4 and IPv6 551
RIB Statistics 551
IPv6 Provider Edge IPv6 and IPv6 VPN Provider Edge Transport over MPLS 552
RIB Quarantining 552
Route and Label Consistency Checker 553
How to Deploy and Monitor RIB 553
Verifying RIB Configuration Using the Routing Table 554
Verifying Networking and Routing Problems 554
Disabling RIB Next-hop Dampening 556
Configuring RCC and LCC 557
Enabling RCC and LCC On-demand Scan 557
Enabling RCC and LCC Background Scan 558
BGP-RIB Feedback Mechanism for Update Generation 559
Configuration Examples for RIB Monitoring 559
Output of show route Command: Example 559
Output of show route backup Command: Example 560
Output of show route best-local Command: Example 560
Output of show route connected Command: Example 560
Output of show route local Command: Example 561
Output of show route longer-prefixes Command: Example 561
Output of show route next-hop Command: Example 561
Enabling RCC and LCC: Example 562
Where to Go Next 562
Additional References 563
Implementing RIP 565C H A P T E R 1 0
Prerequisites for Implementing RIP 566
Information About Implementing RIP 566
RIP Functional Overview 566
Split Horizon for RIP 567
Route Timers for RIP 567
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Contents
Route Redistribution for RIP 567
Default Administrative Distances for RIP 568
Routing Policy Options for RIP 569
Authentication Using Keychain in RIP 569
In-bound RIP Traffic on an Interface 570
Out-bound RIP Traffic on an Interface 571
How to Implement RIP 571
Enabling RIP 571
Customizing RIP 573
Control Routing Information 574
Creating a Route Policy for RIP 576
Configuring RIP Authentication Keychain 577
Configuring RIP Authentication Keychain for IPv4 Interface on a Non-default VRF 577
Configuring RIP Authentication Keychain for IPv4 Interface on Default VRF 579
Configuration Examples for Implementing RIP 580
Configuring a Basic RIP Configuration: Example 580
Configuring RIP on the Provider Edge: Example 580
Adjusting RIP Timers for each VRF Instance: Example 580
Configuring Redistribution for RIP: Example 581
Configuring Route Policies for RIP: Example 582
Configuring Passive Interfaces and Explicit Neighbors for RIP: Example 582
Controlling RIP Routes: Example 583
Configuring RIP Authentication Keychain: Example 583
Additional References 583
Implementing Routing Policy 585C H A P T E R 1 1
Prerequisites for Implementing Routing Policy 586
Restrictions for Implementing Routing Policy 586
Information About Implementing Routing Policy 587
Routing Policy Language 587
Routing Policy Language Overview 587
Routing Policy Language Structure 588
Routing Policy Language Components 597
Routing Policy Language Usage 598
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Contents
Routing Policy Configuration Basics 600
Policy Definitions 600
Parameterization 601
Parameterization at Attach Points 602
Global Parameterization 602
Semantics of Policy Application 603
Boolean Operator Precedence 603
Multiple Modifications of the Same Attribute 603
When Attributes Are Modified 604
Default Drop Disposition 605
Control Flow 605
Policy Verification 606
Policy Statements 607
Remark 607
Disposition 608
Action 610
If 610
Boolean Conditions 611
apply 612
Attach Points 612
BGP Policy Attach Points 613
OSPF Policy Attach Points 638
OSPFv3 Policy Attach Points 642
IS-IS Policy Attach Points 644
EIGRP Policy Attach Points 646
RIP Policy Attach Points 650
PIM Policy Attach Points 652
Nondestructive Editing of Routing Policy 652
Attached Policy Modification 652
Nonattached Policy Modification 653
Editing Routing Policy Configuration Elements 653
Hierarchical Policy Conditions 655
Apply Condition Policies 655
Nested Wildcard Apply Policy 658
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Contents
Wildcards for Route Policy Sets 659
Use Wildcards For Routing Policy Sets 659
VRF Import Policy Enhancement 663
Flexible L3VPN Label Allocation Mode 663
Match Aggregated Route 664
Remove Private AS in Inbound Policy 664
Set Administrative Distance 664
How to Implement Routing Policy 664
Defining a Route Policy 664
Attaching a Routing Policy to a BGP Neighbor 665
Modifying a Routing Policy Using a Text Editor 666
Configuration Examples for Implementing Routing Policy 667
Routing Policy Definition: Example 667
Simple Inbound Policy: Example 668
Modular Inbound Policy: Example 669
Use Wildcards For Routing Policy Sets 670
VRF Import Policy Configuration: Example 674
Additional References 674
Implementing Static Routes 677C H A P T E R 1 2
Prerequisites for Implementing Static Routes 677
Restrictions for Implementing Static Routes 678
Information About Implementing Static Routes 678
Static Route Functional Overview 678
Default Administrative Distance 678
Directly Connected Routes 679
Recursive Static Routes 679
Fully Specified Static Routes 680
Floating Static Routes 680
Default VRF 680
IPv4 and IPv6 Static VRF Routes 680
Dynamic ECMP 681
How to Implement Static Routes 681
Configure Static Route 681
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Contents
Configure Floating Static Route 682
Configure Static Routes Between PE-CE Routers 684
Change Maximum Number of Allowable Static Routes 685
Associate VRF with a Static Route 686
Configuration Examples 687
Configuring Traffic Discard: Example 687
Configuring a Fixed Default Route: Example 688
Configuring a Floating Static Route: Example 688
Configure Native UCMP for Static Routing 688
Configuring a Static Route Between PE-CE Routers: Example 689
Additional References 690
Implementing RCMD 691C H A P T E R 1 3
Route Convergence Monitoring and Diagnostics 691
Configuring Route Convergence Monitoring and Diagnostics 692
Route Convergence Monitoring and Diagnostics Prefix Monitoring 694
Route Convergence Monitoring and Diagnostics OSPF Type 3/5/7 Link-state AdvertisementsMonitoring 695
Enabling RCMD Monitoring for IS-IS Prefixes 695
Enable RCMD Monitoring for OSPF Prefixes 696
Enabling RCMD Monitoring for Type 3/5/7 OSPF LSAs 697
Enabling RCMD Monitoring for IS-IS Prefixes: Example 698
Enabling RCMD Monitoring for OSPF Prefixes: Example 698
Enabling RCMD Monitoring for Type 3/5/7 OSPF LSAs: Example 698
Implementing UCMP 701C H A P T E R 1 4
ECMP vs. UCMP Load Balancing 702
UCMP Minimum Integer Ratio 702
Configuring IS-IS With Weight 703
Configuring IS-IS With Metric 704
Configuring BGP With Weights 705
Configuring TE Tunnel With Weights 706
Policy-Based Tunnel Selection 707
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Contents
Implementing Data Plane Security 721C H A P T E R 1 5
Information about Data Plane Security 721
Source RLOC Decapsulation Filtering 721
EID Instance Membership Distribution 722
Map-Server Membership Gleaning and Distribution 723
Decapsulation Filtering on (P)xTRs 725
TCP-based Reliable Transport Sessions 726
How to Implement Data Plane Security 726
Enable Source RLOC-based Decapsulation Filtering 726
Create, Maintain and Distribute Decapsulation Filter Lists 730
Add or Override Decapsulation Filter List 731
Reset LISP TCP Reliable Transport Session 732
Verify Data Plane Security Configurations 732
Additional References 736
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.xxxvii
Contents
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.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.September 2017
Republished for Release 6.3.2.March 2018
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Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.xxxx
PrefacePreface
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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 6.3.x
Where DocumentedChanged in ReleaseDescriptionFeature
Implementing BGPchapter
Release 6.3.2This feature wasintroduced.
BGP Large Community
Implementing UCMPchapter
Release 6.3.2This feature wasintroduced.
UCMP Minimum IntegerRatio
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Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x2
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 231 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 6.3.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 215 Flow-tag propagation, on page 230 Where to Go Next, on page 231 Additional References, on page 231
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.
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x10
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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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
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x12
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:
Routing Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x13
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
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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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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)#
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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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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
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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(config-bgp-nbrgrp)# advertisement-interval 15RP/0/RSP0/CPU0:router(config-bgp-nbrgrp)# exitRP/0/RSP0/CPU0:router(config-bgp)# neighbor 192.168.1.1RP/0/RSP0/CPU0:router(config-bgp-nbr)# remote-as 1RP/0/RSP0/CPU0:router(config-bgp-nbr)# use neighbor-group AS_1
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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 192.168.1.1
BGP neighbor is 192.168.2.2, 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 n