Reference Guide

Troubleshooting BFD......................................................................................................................................150
9 Border Gateway Protocol IPv4 (BGPv4)..............................................................................153
Autonomous Systems (AS)................................................................................................................................... 153
Sessions and Peers.............................................................................................................................................. 155
Establish a Session........................................................................................................................................ 156
Route Reflectors................................................................................................................................................... 156
Communities...................................................................................................................................................157
BGP Attributes...................................................................................................................................................... 157
Best Path Selection Criteria...........................................................................................................................158
Weight............................................................................................................................................................160
Local Preference............................................................................................................................................160
Multi-Exit Discriminators (MEDs)...................................................................................................................161
Origin.............................................................................................................................................................. 162
AS Path...........................................................................................................................................................163
Next Hop.........................................................................................................................................................163
Multiprotocol BGP................................................................................................................................................ 163
Implement BGP with FTOS....................................................................................................................................164
Additional Path (Add-Path) Support...............................................................................................................164
Advertise IGP Cost as MED for Redistributed Routes....................................................................................164
Ignore Router-ID for Some Best-Path Calculations.......................................................................................165
Four-Byte AS Numbers.................................................................................................................................. 165
AS4 Number Representation..........................................................................................................................165
AS Number Migration.................................................................................................................................... 167
BGP4 Management Information Base (MIB)................................................................................................. 169
Important Points to Remember...................................................................................................................... 169
Configuration Information.....................................................................................................................................170
BGP Configuration................................................................................................................................................ 170
Enabling BGP..................................................................................................................................................171
Configuring AS4 Number Representations.................................................................................................... 174
Configuring Peer Groups................................................................................................................................176
Configuring BGP Fast Fail-Over......................................................................................................................178
Configuring Passive Peering..........................................................................................................................180
Maintaining Existing AS Numbers During an AS Migration...........................................................................181
Allowing an AS Number to Appear in its Own AS Path................................................................................. 181
Enabling Graceful Restart.............................................................................................................................. 182
Enabling Neighbor Graceful Restart.............................................................................................................. 183
Filtering on an AS-Path Attribute................................................................................................................... 184
Regular Expressions as Filters....................................................................................................................... 185
Redistributing Routes..................................................................................................................................... 186
Enabling Additional Paths.............................................................................................................................. 187
Configuring IP Community Lists......................................................................................................................187