Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

Additional Path (Add-Path) Support

The add-path feature reduces convergence times by advertising multiple paths to its peers for the same address prefix without replacing existing paths with new ones. By default, a BGP speaker advertises only the best path to its peers for a given address prefix. If the best path becomes unavailable, the BGP speaker withdraws its path from its local RIB and recalculates a new best path. This situation requires both IGP and BGP convergence and can be a lengthy process.

BGP add-path reduces the time taken for BGP convergence by advertising multiple paths to its peers for the same address prefix without new paths implicitly replacing the existing paths. An iBGP speaker that receives multiple paths from its peers should calculate the best path in its own. BGP add-path helps switchover to next new best path based on IGP convergence time when best path becomes unavailable.