BGP Multipath allows load sharing across multiple EBGP and IBGP paths. A BGP path is considered an equal-cost path (and used for forwarding) if it meets certain conditions. The tie-break is performed after the BGP path selection step, which chooses the next-hop path resolved via the IGP route with the lowest metric. All paths with the same neighboring AS, learned by a multipath-enabled BGP neighbor, are considered for multipath load sharing.

Starting with the Junos OS 23.4R1 release, support for EBGP and IBGP multipath (EIBGP) was introduced. In existing BGP multipath setups, EBGP routes take priority over IBGP routes due to their differing metrics. However, after you enable EIBGP multipath and there is equal load sharing between EBGP and IBGP routes, Junos OS initiates ECMP using a blend of both EBGP and IBGP.

BGP multiple path options must be consistent for all routes forming a BGP multiple path. If BGP multiple path options differ, the multiple path feature chooses a preference, and the multiple path feature might not function as intended.

BGP multipath is supported globally at the [edit protocols bgp] hierarchy level. You can selectively disable multipath on some BGP groups and neighbors. Include disable at [edit protocols bgp group group-name multipath] hierarchy level to disable the multipath option for a group or a specific BGP neighbor.

To enable load-balancing among multiple EBGP paths and multiple IBGP paths , include the multipath statement globally at the [edit protocols bgp] hierarchy level. You cannot enable load-balancing of BGP traffic without including the multipath statement globally, or for a BGP group at the [edit protocols bgp group group-name hierarchy level, or for specific BGP neighbors at the [edit protocols bgp group group-name neighbor address] hierarchy level.

Sample Configuration:

set protocols bgp group external type external 

set protocols bgp group external peer-as 64501

set protocols bgp group external multipath 

set protocols bgp group external neighbor 10.0.1.1 

set protocols bgp group external neighbor 10.0.0.2 

set policy-options policy-statement loadbal from route-filter 10.0.0.0/16 orlonger 

set policy-options policy-statement loadbal then load-balance per-packet 

set routing-options forwarding-table export loadbal

set routing-options autonomous-system 64500