multipath (Protocols BGP)

Syntax

Hierarchy Level

Description

Allow load sharing among multiple EBGP paths and multiple IBGP paths. A path is considered a BGP equal-cost path (and will be used for forwarding) if a tie-break is performed. The tie-break is performed after the BGP route path selection step that chooses the next-hop path that is resolved through the IGP route with the lowest metric. All paths with the same neighboring AS, learned by a multipath-enabled BGP neighbor, are considered.

From 23.4R1 release Junos supports EBGP and IBGP (EIBGP) multipath. In the existing BGP multipath, EBGP routes take priority over IBGP routes because both have different metrics. 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.

Feature-specific policies specify prefixes that support EIBGP multipath. You can configure the policy to choose the prefixes based on any match condition.

Note:

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.

Note:

Starting in Junos OS Release 18.1, 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.

Options

allow-external-internal

Allows IBGP paths to coexist with EBGP paths, and considers both EBGP and IBGP paths equal when path selection between them reaches a point where EBGP paths are preferred.

`allow-protection`	Allows BGP multipath and protection to co-exist. When `allow-protection` is configured there may be a change in `show route` output: N+1 nexthop formation (N ecmp plus 1 backup paths).
`disable`	Disable the multipath option either at the global level for BGP or for a specific group or neighbor and still allow multipath for other groups or neighbors. Before disabling multipath for specific groups or neighbors, ensure that you have enabled multipath at the global level, by configuring the `multipath` statement at the `[edit protocols bgp]` hierarchy level.
`multiple-as`	Disable the default check requiring that paths accepted by BGP multipath must have the same neighboring AS.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.

Release Information

Statement introduced before Junos OS Release 7.4.

disable option introduced in Junos OS Release 18.1R1.

allow-protection option introduced in Junos OS Release 18.4R1.

allow-external-internal option introduced in Junos OS Release 23.4R1.

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