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Table Of Contents
Chapter 9: Border Gateway Protocol IPv4 (BGPv4)................................................................... 155
Autonomous Systems (AS)........................................................................................................................................... 156
Sessions and Peers......................................................................................................................................................... 158
Establish a Session.................................................................................................................................................... 158
Route Reflectors..............................................................................................................................................................158
Communities..................................................................................................................................................................... 159
BGP Attributes.................................................................................................................................................................159
Best Path Selection Criteria....................................................................................................................................159
Weight................................................................................................................................................................................. 161
Local Preference.............................................................................................................................................................. 161
Multi-Exit Discriminators (MEDs)..........................................................................................................................162
Origin.................................................................................................................................................................................. 162
AS Path.............................................................................................................................................................................. 163
Next Hop............................................................................................................................................................................163
Multiprotocol BGP...........................................................................................................................................................163
Implement BGP with Dell Networking OS................................................................................................................. 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)............................................................................................................ 168
Important Points to Remember..............................................................................................................................168
Configuration Information............................................................................................................................................. 169
BGP Configuration.....................................................................................................................................................169
Enabling BGP.................................................................................................................................................................... 170
Configuring AS4 Number Representations................................................................................................................172
Configuring Peer Groups................................................................................................................................................174
Configuring BGP Fast Fall-Over...................................................................................................................................176
Configuring Passive Peering..........................................................................................................................................177
Maintaining Existing AS Numbers During an AS Migration....................................................................................178
Allowing an AS Number to Appear in its Own AS Path.......................................................................................... 178
Enabling Graceful Restart..............................................................................................................................................179
Enabling Neighbor Graceful Restart........................................................................................................................... 180
Filtering on an AS-Path Attribute................................................................................................................................180
Regular Expressions as Filters................................................................................................................................. 181
Filtering BGP Routes Using AS-PATH Information................................................................................................. 183
Redistributing Routes..................................................................................................................................................... 183
Enabling Additional Paths.............................................................................................................................................. 184
Configuring IP Community Lists...................................................................................................................................184
Filtering Routes with Community Lists...................................................................................................................... 185
Manipulating the COMMUNITY Attribute................................................................................................................. 186
Changing MED Attributes..............................................................................................................................................187
Changing the LOCAL_PREFERENCE Attribute.......................................................................................................187
Configuring the local System or a Different System to be the Next Hop for BGP-Learned Routes..........188
Changing the WEIGHT Attribute................................................................................................................................. 188
Enabling Multipath...........................................................................................................................................................189
Filtering BGP Routes Using Route Maps................................................................................................................... 189
Filtering BGP Routes Using AS-PATH Information................................................................................................. 189
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