Network & Infrastructure / EVPN, VXLAN & Data Center Fabrics
EVPN multihoming ESI consistency and duplicate attachments
A dual-homed host receives duplicate traffic or loses connectivity after one uplink changes state. The two leaves may disagree about which Ethernet segment their ports represent.
Environment and inputs: BGP EVPN overlays on a routed underlay; supported route types and multihoming behavior depend on the network OS. Diagnostic/design example; not tested on production equipment.
Collect the evidence
Compare ESI values, redundancy mode, LACP identity, segment membership and Ethernet segment routes. Match each logical attachment to the actual shared downstream device.
Explain the result
ESI identifies a shared Ethernet segment across participating VTEPs. Reusing it for unrelated attachments or assigning different values to the same segment can corrupt multihoming behavior.
Plan the fix
Correct segment identity and supported attachment settings as a coordinated pair change. Keep the downstream aggregation configuration in scope; EVPN cannot compensate for an inconsistent physical bundle.
Check the result and rollback
Test each individual attachment, both active links and restoration while checking duplicates and isolation. Revert if downstream LACP or remote segment state no longer agrees.