Description

This article explains the support for ECMP between EBGP and IBGP.

Symptoms

Starting with 23.4R1 and23.4R1-EVO, ECMP between EBGP and IBGP is supported by using the "allow-external-internal" option.

 

Example configuration:
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# set protocols bgp multipath allow-external-internal
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Solution

For more details, please refer to the multipath (Protocols BGP) page in the Junos CLI Reference or the release notes for 23.4R1 or 23.4R1-EVO.

Below is an excerpt from the CLI Reference.
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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.
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Below is an excerpt from the 23.4R1.
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Support for EIBGP multipath ECMP for defined prefixes (MX Series)—Junos OS Release 23.4R1 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.

To enable EIBGP multipath, configure the allow-external-internal option at the [edit protocols bgp multipath] or [edit logical-systems logical-system-name protocols bgp multipath] hierarchy level.
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Below is an excerpt from the 23.4R1ーEVO.
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Support for EIBGP multipath ECMP for defined prefixes (PTX Series)—Junos OS Evolved Release 23.4R1 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 the EBGP and IBGP routes, Junos OS Evolved 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.

To enable EIBGP multipath, configure the allow-external-internal option at the [edit protocols bgp multipath] or [edit logical-systems logical-system-name protocols bgp multipath] hierarchy level.
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Modification History

2025-09-29 : Minor change and published to public
2025-09-15 : Article Created