Service Manual

9 Border Gateway Protocol IPv4 (BGPv4)......................................................................................................... 166
Autonomous Systems (AS)................................................................................................................................... 166
Sessions and Peers.................................................................................................................................................168
Establish a Session............................................................................................................................................169
Route Reflectors.....................................................................................................................................................169
BGP Attributes......................................................................................................................................................... 170
Best Path Selection Criteria.............................................................................................................................171
Weight................................................................................................................................................................. 173
Local Preference............................................................................................................................................... 173
Multi-Exit Discriminators (MEDs)...................................................................................................................173
Origin...................................................................................................................................................................174
AS Path................................................................................................................................................................ 175
Next Hop.............................................................................................................................................................175
Multiprotocol BGP.................................................................................................................................................. 175
Implement BGP with Dell Networking OS........................................................................................................ 176
Additional Path (Add-Path) Support..............................................................................................................176
Advertise IGP Cost as MED for Redistributed Routes............................................................................... 176
Ignore Router-ID in Best-Path Calculation................................................................................................. 177
Four-Byte AS Numbers.................................................................................................................................... 177
AS4 Number Representation.......................................................................................................................... 177
AS Number Migration.......................................................................................................................................179
BGP4 Management Information Base (MIB)............................................................................................... 181
Important Points to Remember.....................................................................................................................181
Configuration Information................................................................................................................................... 182
BGP Configuration................................................................................................................................................. 182
Enabling BGP..................................................................................................................................................... 183
Configuring AS4 Number Representations.................................................................................................186
Configuring Peer Groups................................................................................................................................ 187
Configuring BGP Fast Fall-Over.................................................................................................................... 190
Configuring Passive Peering........................................................................................................................... 191
Maintaining Existing AS Numbers During an AS Migration...................................................................... 192
Allowing an AS Number to Appear in its Own AS Path.............................................................................193
Enabling Graceful Restart............................................................................................................................... 194
Enabling Neighbor Graceful Restart.............................................................................................................195
Filtering on an AS-Path Attribute...................................................................................................................195
Regular Expressions as Filters........................................................................................................................ 196
Redistributing Routes.......................................................................................................................................198
Enabling Additional Paths............................................................................................................................... 198
Configuring IP Community Lists................................................................................................................... 199
Configuring an IP Extended Community List............................................................................................ 200
Filtering Routes with Community Lists........................................................................................................ 201
Manipulating the COMMUNITY Attribute....................................................................................................201
Changing MED Attributes...............................................................................................................................203
Changing the LOCAL_PREFERENCE Attribute.......................................................................................... 203
Configuring the local System or a Different System to be the Next Hop for BGP-Learned
Routes.................................................................................................................................................................204
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