Users Guide

9 Border Gateway Protocol IPv4 (BGPv4).................................................................................................... 158
Autonomous Systems (AS)...........................................................................................................................................158
Sessions and Peers........................................................................................................................................................ 160
Establish a Session...................................................................................................................................................160
Route Reectors............................................................................................................................................................. 161
BGP Attributes................................................................................................................................................................162
Best Path Selection Criteria....................................................................................................................................162
Weight........................................................................................................................................................................164
Local Preference.......................................................................................................................................................164
Multi-Exit Discriminators (MEDs)...........................................................................................................................165
Origin..........................................................................................................................................................................166
AS Path......................................................................................................................................................................166
Next Hop................................................................................................................................................................... 167
Multiprotocol BGP.......................................................................................................................................................... 167
Implement BGP with Dell Networking OS...................................................................................................................168
Additional Path (Add-Path) Support......................................................................................................................168
Advertise IGP Cost as MED for Redistributed Routes........................................................................................ 168
Ignore Router-ID in Best-Path Calculation............................................................................................................ 169
Four-Byte AS Numbers........................................................................................................................................... 169
AS4 Number Representation.................................................................................................................................. 169
AS Number Migration............................................................................................................................................... 171
BGP4 Management Information Base (MIB)........................................................................................................172
Important Points to Remember.............................................................................................................................. 172
Conguration Information..............................................................................................................................................173
BGP Conguration..........................................................................................................................................................173
Enabling BGP.............................................................................................................................................................174
Conguring AS4 Number Representations............................................................................................................177
Conguring Peer Groups......................................................................................................................................... 178
Conguring BGP Fast Fall-Over..............................................................................................................................181
Conguring Passive Peering................................................................................................................................... 182
Maintaining Existing AS Numbers During an AS Migration................................................................................. 183
Allowing an AS Number to Appear in its Own AS Path....................................................................................... 184
Enabling Graceful Restart....................................................................................................................................... 185
Enabling Neighbor Graceful Restart...................................................................................................................... 186
Filtering on an AS-Path Attribute........................................................................................................................... 186
Regular Expressions as Filters................................................................................................................................. 187
Redistributing Routes...............................................................................................................................................189
Enabling Additional Paths........................................................................................................................................ 189
Conguring IP Community Lists.............................................................................................................................190
Conguring an IP Extended Community List.........................................................................................................191
Filtering Routes with Community Lists.................................................................................................................. 192
Manipulating the COMMUNITY Attribute.............................................................................................................192
Changing MED Attributes....................................................................................................................................... 194
Changing the LOCAL_PREFERENCE Attribute.................................................................................................. 194
Changing the NEXT_HOP Attribute......................................................................................................................195
Changing the WEIGHT Attribute............................................................................................................................195
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