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Systems & Data Center · Advanced

Ethernet Segment Identifier (ESI)

A 10-byte EVPN identifier for a set of links connecting a device to multiple PE or leaf switches, enabling all-active multihoming.

Definition

ESI-LAG lets a server attach to two or more leaves with one LAG without vPC or MC-LAG peer links. EVPN route types 1 and 4 handle aliasing, mass withdrawal and designated forwarder election.

Example

A server bonds to leaf1 and leaf2 sharing ESI 00:01:01:01:01:01:01:01:01:01 with the same LACP system ID.

Exam tip

ESI-LAG is the standards-based alternative to MC-LAG and vPC; it needs no inter-switch peer link.

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