Reference Guide

Configure BFD for VRRP......................................................................................................................................... 122
Configuring Protocol Liveness................................................................................................................................125
Chapter 9: Border Gateway Protocol IPv4 (BGPv4)....................................................................126
Autonomous Systems (AS)........................................................................................................................................... 126
Sessions and Peers..........................................................................................................................................................128
Establish a Session.................................................................................................................................................... 128
Route Reflectors..............................................................................................................................................................129
BGP Attributes................................................................................................................................................................. 130
Best Path Selection Criteria....................................................................................................................................130
Weight.......................................................................................................................................................................... 132
Local Preference........................................................................................................................................................ 132
Multi-Exit Discriminators (MEDs).......................................................................................................................... 133
Origin.............................................................................................................................................................................134
AS Path........................................................................................................................................................................ 134
Next Hop......................................................................................................................................................................135
Multiprotocol BGP...........................................................................................................................................................135
Implement BGP ............................................................................................................................................................... 135
Advertise IGP Cost as MED for Redistributed Routes..................................................................................... 136
Ignore Router-ID for Some Best-Path Calculations.......................................................................................... 136
Four-Byte AS Numbers............................................................................................................................................ 136
AS4 Number Representation...................................................................................................................................137
AS Number Migration............................................................................................................................................... 138
BGP4 Management Information Base (MIB)...................................................................................................... 139
Important Points to Remember..............................................................................................................................140
Configuration Information..............................................................................................................................................140
BGP Configuration........................................................................................................................................................... 141
Enabling BGP............................................................................................................................................................... 141
Configuring AS4 Number Representations..........................................................................................................144
Configuring Peer Groups..........................................................................................................................................146
Configuring BGP Fast Fail-Over.............................................................................................................................148
Configuring Passive Peering................................................................................................................................... 149
Maintaining Existing AS Numbers During an AS Migration............................................................................. 150
Allowing an AS Number to Appear in its Own AS Path.....................................................................................151
Enabling Neighbor Graceful Restart...................................................................................................................... 151
Filtering on an AS-Path Attribute.......................................................................................................................... 152
Regular Expressions as Filters................................................................................................................................ 153
Redistributing Routes............................................................................................................................................... 154
Enabling Additional Paths........................................................................................................................................ 155
Configuring IP Community Lists.............................................................................................................................155
Configuring an IP Extended Community List...................................................................................................... 156
Filtering Routes with Community Lists.................................................................................................................157
Manipulating the COMMUNITY Attribute............................................................................................................157
Changing MED Attributes........................................................................................................................................159
Changing the LOCAL_PREFERENCE Attribute.................................................................................................159
Changing the NEXT_HOP Attribute..................................................................................................................... 160
Changing the WEIGHT Attribute........................................................................................................................... 160
Enabling Multipath.....................................................................................................................................................160
Filtering BGP Routes................................................................................................................................................. 161
Filtering BGP Routes Using Route Maps............................................................................................................. 162
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