Cisco ASR 9000 Series User manual

Cisco ASR 9000 Series Aggregation Services Router Routing
Configuration Guide, Release 5.3.x
First Published: 2015-01-12
Last Modified: 2015-09-03
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CONTENTS
Preface Preface xxix
Obtaining Documentation and Submitting a Service Request xxix
CHAPTER 1 New and Changed Routing Features 1
New and Changed Routing Feature Information 1
CHAPTER 2 Implementing BGP 5
Prerequisites for Implementing BGP 7
Information About Implementing BGP 8
BGP Functional Overview 8
BGP Router Identifier 8
BGP Maximum Prefix - Discard Extra Paths 9
Restrictions 9
BGP Default Limits 10
BGP Next Hop Tracking 11
Scoped IPv4/VPNv4 Table Walk 12
Reordered Address Family Processing 12
New Thread for Next-Hop Processing 12
show, clear, and debug Commands 12
Autonomous System Number Formats in BGP 13
2-byte Autonomous System Number Format 13
4-byte Autonomous System Number Format 13
as-format Command 13
BGP Configuration 13
Configuration Modes 14
Router Configuration Mode 14
Router Address Family Configuration Mode 14
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Neighbor Configuration Mode 14
Neighbor Address Family Configuration Mode 14
VRF Configuration Mode 14
VRF Address Family Configuration Mode 15
Configuring Resilient Per-CE Label Allocation Mode Under VRF Address
Family 15
Configuring Resilient Per-CE Label Allocation Mode Using a
Route-Policy 17
VRF Neighbor Configuration Mode 18
VRF Neighbor Address Family Configuration Mode 18
VPNv4 Address Family Configuration Mode 18
L2VPN Address Family Configuration Mode 19
Neighbor Submode 19
Configuration Templates 20
Template Inheritance Rules 21
Viewing Inherited Configurations 24
show bgp neighbors 25
show bgp af-group 26
show bgp session-group 27
show bgp neighbor-group 28
No Default Address Family 29
Neighbor Address Family Combinations 29
Routing Policy Enforcement 30
Table Policy 31
Update Groups 32
BGP Update Generation and Update Groups 32
BGP Update Group 32
BGP Cost Community 32
How BGP Cost Community Influences the Best Path Selection Process 33
Cost Community Support for Aggregate Routes and Multipaths 34
Influencing Route Preference in a Multiexit IGP Network 35
BGP Cost Community Support for EIGRP MPLS VPN PE-CE with Back-door
Links 36
Adding Routes to the Routing Information Base 37
BGP DMZ Aggregate Bandwidth 37
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Configuring BGP DMZ Aggregate Bandwidth: Example 38
Configuring Policy-based Link Bandwidth: Example 39
BGP Best Path Algorithm 39
Comparing Pairs of Paths 40
Order of Comparisons 42
Best Path Change Suppression 42
Administrative Distance 43
Multiprotocol BGP 44
Route Dampening 46
Minimizing Flapping 47
BGP Routing Domain Confederation 47
BGP Route Reflectors 47
RPL - if prefix is-best-path/is-best-multipath 51
Default Address Family for show Commands 52
TCP Maximum Segment Size 52
Per Neighbor TCP MSS 52
MPLS VPN Carrier Supporting Carrier 53
BGP Keychains 54
BGP Nonstop Routing 54
BGP Local Label Retention 55
Command Line Interface (CLI) Consistency for BGP Commands 55
BGP Additional Paths 56
iBGP Multipath Load Sharing 56
BGP Selective Multipath 57
Accumulated Interior Gateway Protocol Attribute 58
Per VRF and Per CE Label for IPv6 Provider Edge 59
IPv4 BGP-Policy Accounting on Cisco ASR 9000's A9K-SIP-700 59
IPv6 Unicast Routing on Cisco ASR 9000's A9K-SIP-700 59
IPv6 uRPF Support on Cisco ASR 9000's A9K-SIP-700 60
Remove and Replace Private AS Numbers from AS Path in BGP 60
Selective VRF Download 61
Line Card Roles and Filters in Selective VRF Download 61
Selective VRF Download Disable 62
Calculating Routes Downloaded to Line Card with or without SVD 62
BGP Accept Own 63
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BGP DMZ Link Bandwidth for Unequal Cost Recursive Load Balancing 65
BFD Multihop Support for BGP 65
BGP Multi-Instance and Multi-AS 65
BGP Prefix Origin Validation Based on RPKI 66
Configuring RPKI Cache-server 66
Configuring RPKI Prefix Validation 69
Configuring RPKI Bestpath Computation 70
BGP 3107 PIC Updates for Global Prefixes 71
BGP Prefix Independent Convergence for RIB and FIB 72
BGP Update Message Error Handling 72
BGP Attribute Filtering 73
BGP Attribute Filter Actions 73
BGP Error Handling and Attribute Filtering Syslog Messages 73
BGP Link-State 74
BGP Permanent Network 74
BGP-RIB Feedback Mechanism for Update Generation 75
BGP VRF Dynamic Route Leaking 75
User Defined Martian Check 76
Resilient Per-CE Label Allocation Mode 77
BGP Multipath Enhancements 77
MVPN with BGP SAFI-2 and SAFI-129 77
BGP Monitoring Protocol 78
How to Implement BGP 79
Enabling BGP Routing 79
Configuring Multiple BGP Instances for a Specific Autonomous System 81
Configuring a Routing Domain Confederation for BGP 82
Resetting an eBGP Session Immediately Upon Link Failure 83
Logging Neighbor Changes 84
Adjusting BGP Timers 84
Changing the BGP Default Local Preference Value 85
Configuring the MED Metric for BGP 86
Configuring BGP Weights 86
Tuning the BGP Best-Path Calculation 88
Indicating BGP Back-door Routes 89
Configuring Aggregate Addresses 90
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Redistributing iBGP Routes into IGP 91
Configuring Discard Extra Paths 92
Configuring Per Neighbor TCP MSS 93
Disabling Per Neighbor TCP MSS 95
Redistributing Prefixes into Multiprotocol BGP 98
Configuring BGP Route Dampening 100
Applying Policy When Updating the Routing Table 105
Setting BGP Administrative Distance 106
Configuring a BGP Neighbor Group and Neighbors 106
Configuring a Route Reflector for BGP 109
Configuring BGP Route Filtering by Route Policy 110
Configuring BGP Attribute Filtering 112
Configuring BGP Next-Hop Trigger Delay 113
Disabling Next-Hop Processing on BGP Updates 114
Configuring BGP Community and Extended-Community Advertisements 115
Configuring the BGP Cost Community 117
Configuring Software to Store Updates from a Neighbor 120
BGP Persistence 122
BGP Persistence Configuration: Example 123
BGP Graceful Maintenance 123
Restrictions for BGP Graceful Maintenance 123
Graceful Maintenance Operation 124
Inter Autonomous System 124
No Automatic Shutdown 125
When to Shut Down After Graceful Maintenance 125
Activate Graceful Maintenance under BGP Router (All Neighbors) 125
Activate Graceful Maintenance on a Single Neighbor 127
Activate Graceful Maintenance on a Group of Neighbors 127
Direct Router to Reduce Route Preference 129
Bring Router or Link Back into Service 130
Show Command Outputs to Verify BGP Graceful Maintenance 130
L3VPN iBGP PE-CE 131
L3VPN iBGP PE-CE Overview 131
Restrictions for L3VPN iBGP PE-CE 132
Configuring L3VPN iBGP PE-CE 133
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Flow-tag propagation 135
Restrictions for flow-tag propagation 135
Source and destination-based flow tag 135
Configure Source and Destination-based Flow Tag 135
Configuring a VPN Routing and Forwarding Instance in BGP 137
Defining Virtual Routing and Forwarding Tables in Provider Edge Routers 137
Configuring the Route Distinguisher 139
Configuring PE-PE or PE-RR Interior BGP Sessions 140
Configuring Route Reflector to Hold Routes That Have a Defined Set of RT
Communities 143
Configuring BGP as a PE-CE Protocol 144
Redistribution of IGPs to BGP 148
Configuring Keychains for BGP 150
Disabling a BGP Neighbor 151
Resetting Neighbors Using BGP Inbound Soft Reset 152
Resetting Neighbors Using BGP Outbound Soft Reset 153
Resetting Neighbors Using BGP Hard Reset 154
Clearing Caches, Tables, and Databases 155
Displaying System and Network Statistics 156
Displaying BGP Process Information 157
Monitoring BGP Update Groups 159
Configuring BGP Nonstop Routing 160
Disable BGP Nonstop Routing 160
Re-enable BGP Nonstop Routing 161
Installing Primary Backup Path for Prefix Independent Convergence (PIC) 161
Retaining Allocated Local Label for Primary Path 163
Configuring BGP Additional Paths 163
Configuring iBGP Multipath Load Sharing 165
Originating Prefixes with AiGP 166
Configuring BGP Accept Own 168
Configuring BGP Link-State 169
Configuring BGP Link-state 169
Configuring Domain Distinguisher 170
Configuring BGP Permanent Network 171
Configuring BGP Permanent Network 171
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How to Advertise Permanent Network 173
Enabling BGP Unequal Cost Recursive Load Balancing 174
Configuring VRF Dynamic Route Leaking 176
Enabling Selective VRF Download 177
Disabling Selective VRF Download 179
Configuring Resilient Per-CE Label Allocation Mode 181
Configuring Resilient Per-CE Label Allocation Mode Under VRF Address Family 181
Configuring Resilient Per-CE Label Allocation Mode Using a Route-Policy 183
Configuration Examples for Implementing BGP 184
Enabling BGP: Example 184
Displaying BGP Update Groups: Example 186
BGP Neighbor Configuration: Example 186
BGP Confederation: Example 187
BGP Route Reflector: Example 188
BGP Nonstop Routing Configuration: Example 189
Primary Backup Path Installation: Example 189
Allocated Local Label Retention: Example 189
iBGP Multipath Loadsharing Configuration: Example 189
Discard Extra Paths Configuration: Example 190
Displaying Discard Extra Paths Information: Example 190
Configure Per Neighbor TCP MSS: Examples 191
Verify Per Neighbor TCP MSS: Examples 192
Originating Prefixes With AiGP: Example 194
BGP Accept Own Configuration: Example 195
BGP Unequal Cost Recursive Load Balancing: Example 195
VRF Dynamic Route Leaking Configuration: Example 197
Resilient Per-CE Label Allocation Mode Configuration: Example 198
Configuring Resilient Per-CE Label Allocation Mode Under VRF Address Family:
Example 198
Configuring Resilient Per-CE Label Allocation Mode Using a Route-Policy: Example 198
Where to Go Next 198
Additional References 198
CHAPTER 3 Implementing BGP Flowspec 203
BGP Flow Specification 203
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Limitations 204
BGP Flowspec Conceptual Architecture 204
Information About Implementing BGP Flowspec 205
Flow Specifications 206
Supported Matching Criteria and Actions 206
Traffic Filtering Actions 209
BGP Flowspec Client-Server (Controller) Model and Configuration 211
How to Configure BGP Flowspec 212
Enable Flowspec on BGP Side 213
Define Class 214
Define Policy Map 215
Link Flowspec to PBR Policies 217
Verify BGP Flowspec 219
Preserving Redirect Nexthop 221
Validate BGP Flowspec 222
Disabling BGP Flowspec 223
Disable Flowspec Redirect and Validation 223
Configuration Examples for Implementing BGP Flowspec 225
Flowspec Rule Configuration 225
Drop Packet Length 226
Remark DSCP 226
Additional References for BGP Flowspec 227
CHAPTER 4 Implementing BFD 229
Prerequisites for Implementing BFD 231
Restrictions for Implementing BFD 232
Information About BFD 233
Differences in BFD in Cisco IOS XR Software and Cisco IOS Software 233
BFD Multipath Sessions Support on nV Edge System 234
BFD Modes of Operation 234
BFD Packet Information 235
BFD Source and Destination Ports 235
BFD Packet Intervals and Failure Detection 235
BFD Packet Intervals on Physical Interfaces 235
BFD Packet Intervals on Bundle Member Links 236
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