Users Guide

9 Border Gateway Protocol IPv4 (BGPv4).................................................................................................... 162
Autonomous Systems (AS)........................................................................................................................................... 162
Sessions and Peers........................................................................................................................................................ 164
Establish a Session................................................................................................................................................... 164
Route Reectors.............................................................................................................................................................165
BGP Attributes................................................................................................................................................................166
Best Path Selection Criteria....................................................................................................................................166
Weight........................................................................................................................................................................168
Local Preference.......................................................................................................................................................168
Multi-Exit Discriminators (MEDs)...........................................................................................................................169
Origin..........................................................................................................................................................................170
AS Path.......................................................................................................................................................................171
Next Hop.................................................................................................................................................................... 171
Multiprotocol BGP...........................................................................................................................................................171
Implement BGP with Dell Networking OS...................................................................................................................172
Additional Path (Add-Path) Support......................................................................................................................172
Advertise IGP Cost as MED for Redistributed Routes.........................................................................................172
Ignore Router-ID in Best-Path Calculation............................................................................................................ 173
Four-Byte AS Numbers............................................................................................................................................173
AS4 Number Representation.................................................................................................................................. 173
AS Number Migration.............................................................................................................................................. 175
BGP4 Management Information Base (MIB)........................................................................................................176
Important Points to Remember.............................................................................................................................. 176
Conguration Information.............................................................................................................................................. 177
BGP Conguration..........................................................................................................................................................177
Enabling BGP............................................................................................................................................................ 178
Conguring AS4 Number Representations............................................................................................................181
Conguring Peer Groups......................................................................................................................................... 183
Conguring BGP Fast Fall-Over.............................................................................................................................185
Conguring Passive Peering....................................................................................................................................187
Maintaining Existing AS Numbers During an AS Migration................................................................................. 187
Allowing an AS Number to Appear in its Own AS Path....................................................................................... 188
Enabling Graceful Restart........................................................................................................................................189
Enabling Neighbor Graceful Restart...................................................................................................................... 190
Filtering on an AS-Path Attribute........................................................................................................................... 190
Regular Expressions as Filters.................................................................................................................................192
Redistributing Routes...............................................................................................................................................193
Enabling Additional Paths........................................................................................................................................ 194
Conguring IP Community Lists............................................................................................................................. 194
Conguring an IP Extended Community List........................................................................................................195
Filtering Routes with Community Lists..................................................................................................................196
Manipulating the COMMUNITY Attribute............................................................................................................. 197
Changing MED Attributes....................................................................................................................................... 198
Changing the LOCAL_PREFERENCE Attribute.................................................................................................. 198
Conguring the local System or a Dierent System to be the Next Hop for BGP-Learned Routes............. 199
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