Users Guide

7 Bidirectional Forwarding Detection (BFD).................................................................................................. 148
How BFD Works............................................................................................................................................................. 148
BFD Packet Format..................................................................................................................................................149
BFD Sessions............................................................................................................................................................ 150
BFD Three-Way Handshake.....................................................................................................................................151
Session State Changes............................................................................................................................................153
Important Points to Remember.................................................................................................................................... 153
Congure BFD................................................................................................................................................................ 153
Congure BFD for Physical Ports...........................................................................................................................154
Congure BFD for Static Routes............................................................................................................................155
Congure BFD for IPv6 Static Routes...................................................................................................................158
Congure BFD for OSPF.........................................................................................................................................160
Congure BFD for OSPFv3.....................................................................................................................................164
Congure BFD for IS-IS........................................................................................................................................... 167
Congure BFD for BGP...........................................................................................................................................169
Congure BFD for VRRP.........................................................................................................................................175
Conguring Protocol Liveness................................................................................................................................ 178
8 Border Gateway Protocol IPv4 (BGPv4).....................................................................................................179
Autonomous Systems (AS)........................................................................................................................................... 179
Sessions and Peers......................................................................................................................................................... 181
Establish a Session....................................................................................................................................................181
Route Reectors.............................................................................................................................................................182
Communities............................................................................................................................................................. 183
BGP Attributes................................................................................................................................................................183
Best Path Selection Criteria....................................................................................................................................183
Weight........................................................................................................................................................................185
Local Preference.......................................................................................................................................................185
Multi-Exit Discriminators (MEDs)...........................................................................................................................186
Origin.......................................................................................................................................................................... 187
AS Path...................................................................................................................................................................... 187
Next Hop................................................................................................................................................................... 188
Multiprotocol BGP..........................................................................................................................................................188
Implement BGP ..............................................................................................................................................................188
Additional Path (Add-Path) Support......................................................................................................................188
Advertise IGP Cost as MED for Redistributed Routes........................................................................................ 189
Ignore Router-ID for Some Best-Path Calculations............................................................................................. 189
Four-Byte AS Numbers............................................................................................................................................189
AS4 Number Representation..................................................................................................................................190
AS Number Migration............................................................................................................................................... 191
BGP4 Management Information Base (MIB)........................................................................................................193
Important Points to Remember.............................................................................................................................. 193
Conguration Information..............................................................................................................................................194
BGP Conguration......................................................................................................................................................... 194
Enabling BGP............................................................................................................................................................ 195
Contents
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