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Conguring BGP4 (IPv4).............................................................................................................................................................................................351

BGP4 overview.....................................................................................................................................................................................................................................351

Relationship between the BGP4 route table and the IP route table......................................................................................................................352

How BGP4 selects a path for a route (BGP best path selection algorithm)...................................................................................................... 353

BGP4 message types.............................................................................................................................................................................................................. 354

Grouping of RIB-out peers.....................................................................................................................................................................................................356

Implementation of BGP4................................................................................................................................................................................................................. 356

BGP4 restart..........................................................................................................................................................................................................................................356

BGP4 Peer notication during a management module switchover......................................................................................................................357

BGP4 neighbor local AS.........................................................................................................................................................................................................358

Basic conguration and activation for BGP4...........................................................................................................................................................................360

Disabling BGP4.......................................................................................................................................................................................................................... 361

BGP4 parameters................................................................................................................................................................................................................................361

Parameter changes that take eect immediately..........................................................................................................................................................363

Parameter changes that take eect after resetting neighbor sessions.................................................................................................................363

Parameter changes that take eect after disabling and re-enabling redistribution.........................................................................................364

Memory considerations.....................................................................................................................................................................................................................364

Memory conguration options obsoleted by dynamic memory............................................................................................................................ 364

Basic conguration tasks required for BGP4...........................................................................................................................................................................364

Enabling BGP4 on the device...............................................................................................................................................................................................365

Changing the device ID............................................................................................................................................................................................................365

Setting the local AS number.................................................................................................................................................................................................. 365

Adding a loopback interface...................................................................................................................................................................................................366

Adding BGP4 neighbors.........................................................................................................................................................................................................367

Adding a BGP4 peer group................................................................................................................................................................................................... 374

Optional BGP4 conguration tasks............................................................................................................................................................................................. 377

Changing the Keep Alive Time and Hold Time..............................................................................................................................................................377

Changing the BGP4 next-hop update timer...................................................................................................................................................................377

Enabling fast external fallover................................................................................................................................................................................................378

Changing the maximum number of paths for BGP4 Multipath load sharing...................................................................................................378

Customizing BGP4 Multipath load sharing.....................................................................................................................................................................380

Specifying a list of networks to advertise......................................................................................................................................................................... 380

Changing the default local preference................................................................................................................................................................................381

Using the IP default route as a valid next-hop for a BGP4 route...........................................................................................................................382

Changing the default MED (Metric) used for route redistribution...........................................................................................................................382

Enabling next-hop recursion..................................................................................................................................................................................................382

Changing administrative distances......................................................................................................................................................................................385

Requiring the rst AS to be the neighbor AS..................................................................................................................................................................386

Disabling or re-enabling comparison of the AS-Path length...................................................................................................................................387

Enabling or disabling comparison of device IDs...........................................................................................................................................................387

Conguring the device to always compare Multi-Exit Discriminators.................................................................................................................. 387

Treating missing MEDs as the worst MEDs....................................................................................................................................................................388

Conguring route reection parameters........................................................................................................................................................................... 388

Conguring confederations.................................................................................................................................................................................................... 391

Aggregating routes advertised to BGP4 neighbors.....................................................................................................................................................394

Conguring BGP4 restart.................................................................................................................................................................................................................395

Conguring BGP4 Restart for the global routing instance....................................................................................................................................... 395

Conguring BGP4 Restart for a VRF................................................................................................................................................................................ 395

Conguring timers for BGP4 Restart (optional).............................................................................................................................................................395

BGP4 null0 routing....................................................................................................................................................................................................................396

FastIron Ethernet Switch Layer 3 Routing

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