Best Path Selection Criteria.........................................................................................................155
Weight.......................................................................................................................................... 157
Local Preference..........................................................................................................................157
Multi-Exit Discriminators (MEDs)................................................................................................ 158
Origin........................................................................................................................................... 159
AS Path.........................................................................................................................................160
Next Hop..................................................................................................................................... 160
Multiprotocol BGP............................................................................................................................ 160
Implement BGP ................................................................................................................................ 161
Additional Path (Add-Path) Support............................................................................................161
Advertise IGP Cost as MED for Redistributed Routes.................................................................161
Ignore Router-ID for Some Best-Path Calculations..................................................................162
Four-Byte AS Numbers............................................................................................................... 162
AS4 Number Representation...................................................................................................... 162
AS Number Migration..................................................................................................................164
BGP4 Management Information Base (MIB).............................................................................. 166
Important Points to Remember..................................................................................................166
Configuration Information................................................................................................................167
BGP Configuration............................................................................................................................ 167
Enabling BGP...............................................................................................................................168
Configuring AS4 Number Representations................................................................................ 172
Configuring Peer Groups............................................................................................................ 173
Configuring BGP Fast Fail-Over..................................................................................................176
Configuring Passive Peering....................................................................................................... 178
Maintaining Existing AS Numbers During an AS Migration........................................................ 179
Allowing an AS Number to Appear in its Own AS Path..............................................................180
Enabling Neighbor Graceful Restart...........................................................................................180
Filtering on an AS-Path Attribute................................................................................................ 181
Regular Expressions as Filters..................................................................................................... 183
Redistributing Routes..................................................................................................................184
Enabling Additional Paths............................................................................................................185
Configuring IP Community Lists.................................................................................................185
Configuring an IP Extended Community List.............................................................................187
Filtering Routes with Community Lists.......................................................................................188
Manipulating the COMMUNITY Attribute...................................................................................188
Changing MED Attributes........................................................................................................... 190
Changing the LOCAL_PREFERENCE Attribute.......................................................................... 190
Changing the NEXT_HOP Attribute............................................................................................191
Changing the WEIGHT Attribute.................................................................................................192
Enabling Multipath.......................................................................................................................192
Filtering BGP Routes....................................................................................................................192
Filtering BGP Routes Using Route Maps.................................................................................... 194