How BFD Works.............................................................................................................................................................. 110
BFD Packet Format....................................................................................................................................................111
BFD Sessions.............................................................................................................................................................112
BFD Three-Way Handshake.......................................................................................................................................113
Session State Changes..............................................................................................................................................115
Important Points to Remember....................................................................................................................................... 115
Congure BFD.................................................................................................................................................................115
Congure BFD for Physical Ports.............................................................................................................................. 116
Congure BFD for Static Routes............................................................................................................................... 119
Congure BFD for OSPF.......................................................................................................................................... 120
Congure BFD for OSPFv3.......................................................................................................................................122
Congure BFD for IS-IS............................................................................................................................................ 124
Congure BFD for BGP............................................................................................................................................ 125
Congure BFD for VRRP.......................................................................................................................................... 132
Conguring Protocol Liveness...................................................................................................................................134
Troubleshooting BFD.................................................................................................................................................134
8 Border Gateway Protocol IPv4 (BGPv4)...................................................................... 136
Autonomous Systems (AS).............................................................................................................................................136
Sessions and Peers......................................................................................................................................................... 138
Establish a Session....................................................................................................................................................138
Route Reectors.............................................................................................................................................................139
BGP Attributes............................................................................................................................................................... 140
Best Path Selection Criteria......................................................................................................................................140
Weight...................................................................................................................................................................... 142
Local Preference.......................................................................................................................................................142
Multi-Exit Discriminators (MEDs)..............................................................................................................................143
Origin........................................................................................................................................................................ 144
AS Path.....................................................................................................................................................................144
Next Hop.................................................................................................................................................................. 145
Multiprotocol BGP.......................................................................................................................................................... 145
Implement BGP with Dell Networking OS....................................................................................................................... 146
Additional Path (Add-Path) Support......................................................................................................................... 146
Advertise IGP Cost as MED for Redistributed Routes...............................................................................................146
Ignore Router-ID for Some Best-Path Calculations................................................................................................... 147
Four-Byte AS Numbers.............................................................................................................................................147
AS4 Number Representation.....................................................................................................................................147
AS Number Migration............................................................................................................................................... 149
BGP4 Management Information Base (MIB)............................................................................................................ 150
Important Points to Remember.................................................................................................................................150
Conguration Information................................................................................................................................................ 151
BGP Conguration...........................................................................................................................................................151
Enabling BGP............................................................................................................................................................152
Conguring AS4 Number Representations............................................................................................................... 155
Conguring Peer Groups...........................................................................................................................................157
Conguring BGP Fast Fall-Over................................................................................................................................159
6