Setup Guide

7 Bidirectional Forwarding Detection (BFD).................................................................................................. 150
How BFD Works............................................................................................................................................................. 150
BFD Packet Format.................................................................................................................................................. 151
BFD Sessions............................................................................................................................................................ 152
BFD Three-Way Handshake.................................................................................................................................... 153
Session State Changes............................................................................................................................................155
Important Points to Remember.................................................................................................................................... 155
Congure BFD................................................................................................................................................................ 155
Congure BFD for Physical Ports...........................................................................................................................156
Congure BFD for Static Routes............................................................................................................................157
Congure BFD for IPv6 Static Routes...................................................................................................................160
Congure BFD for OSPF.........................................................................................................................................162
Congure BFD for OSPFv3.....................................................................................................................................166
Congure BFD for IS-IS...........................................................................................................................................169
Congure BFD for BGP............................................................................................................................................171
Congure BFD for VRRP......................................................................................................................................... 177
Conguring Protocol Liveness................................................................................................................................ 180
8 Border Gateway Protocol IPv4 (BGPv4)..................................................................................................... 181
Autonomous Systems (AS)............................................................................................................................................181
Sessions and Peers.........................................................................................................................................................183
Establish a Session................................................................................................................................................... 183
Route Reectors.............................................................................................................................................................184
Communities............................................................................................................................................................. 185
BGP Attributes................................................................................................................................................................185
Best Path Selection Criteria....................................................................................................................................185
Weight........................................................................................................................................................................187
Local Preference....................................................................................................................................................... 187
Multi-Exit Discriminators (MEDs)...........................................................................................................................188
Origin..........................................................................................................................................................................189
AS Path......................................................................................................................................................................189
Next Hop................................................................................................................................................................... 190
Multiprotocol BGP..........................................................................................................................................................190
Implement BGP ............................................................................................................................................................. 190
Additional Path (Add-Path) Support......................................................................................................................190
Advertise IGP Cost as MED for Redistributed Routes.........................................................................................191
Ignore Router-ID for Some Best-Path Calculations.............................................................................................. 191
Four-Byte AS Numbers............................................................................................................................................ 191
AS4 Number Representation.................................................................................................................................. 192
AS Number Migration.............................................................................................................................................. 193
BGP4 Management Information Base (MIB)........................................................................................................195
Important Points to Remember.............................................................................................................................. 195
Conguration Information..............................................................................................................................................196
BGP Conguration......................................................................................................................................................... 196
Enabling BGP............................................................................................................................................................ 197
Contents
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