Reference Guide
Implementation Information....................................................................................................... 111
Configuration Task List for Prefix Lists........................................................................................ 111
ACL Resequencing.............................................................................................................................115
Resequencing an ACL or Prefix List............................................................................................ 116
Route Maps........................................................................................................................................ 117
Implementation Information....................................................................................................... 117
Flow-Based Monitoring Support for ACLs........................................................................................118
Behavior of Flow-Based Monitoring...........................................................................................118
Enabling Flow-Based Monitoring............................................................................................... 120
7 Bidirectional Forwarding Detection (BFD)..................................................... 122
How BFD Works................................................................................................................................ 122
BFD Packet Format......................................................................................................................123
BFD Sessions................................................................................................................................125
BFD Three-Way Handshake........................................................................................................125
Session State Changes................................................................................................................ 126
Important Points to Remember........................................................................................................127
Configure BFD................................................................................................................................... 127
Configure BFD for Physical Ports............................................................................................... 128
Configure BFD for Static Routes................................................................................................. 131
Configure BFD for OSPF............................................................................................................. 133
Configure BFD for OSPFv3..........................................................................................................136
Configure BFD for IS-IS...............................................................................................................137
Configure BFD for BGP...............................................................................................................140
Configure BFD for VRRP..............................................................................................................147
Configuring Protocol Liveness................................................................................................... 150
Troubleshooting BFD.................................................................................................................. 150
8 Border Gateway Protocol IPv4 (BGPv4)......................................................... 152
Autonomous Systems (AS)................................................................................................................152
Sessions and Peers............................................................................................................................154
Establish a Session.......................................................................................................................155
Route Reflectors................................................................................................................................155
BGP Attributes................................................................................................................................... 156
Best Path Selection Criteria.........................................................................................................157
Weight..........................................................................................................................................159
Local Preference......................................................................................................................... 159
Multi-Exit Discriminators (MEDs)................................................................................................160
Origin............................................................................................................................................161
AS Path.........................................................................................................................................162
Next Hop......................................................................................................................................162
Multiprotocol BGP.............................................................................................................................163