Selecting Multiple Equal-Cost Active Paths

You can configure BGP to select multiple equal-cost EBGP or IBGP paths as active paths. Selecting multiple paths allows BGP peerings to load-balance traffic across an AS-confederation boundary. The Junos OS BGP multipath supports the following:

Load balancing across multiple links between two routing devices belonging to different ASs
Load balancing across a common subnet or multiple subnets to different routing devices belonging to the same peer AS
Load balancing across multiple links between two routing devices belonging to different external confederation peers
Load balancing across a common subnet or multiple subnets to different routing devices belonging to external confederation peers

To configure a BGP multipath, include the multipath statement:

multipath {multiple-as;}

To disable the default check requiring that paths accepted by BGP multipath must have the same neighboring AS, include the multiple-as option.

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.