According to RFC 7432, specific Ethernet Segment Identifier (ESI) types support auto-derivation and the 10-byte ESI value does not need to be configured. SR OS supports the manual configuration of 10-byte ESI for the Ethernet segment, or alternatively, the auto-derivation of EVPN type 1 ESIs.
The auto-esi {none|type-1} command is supported in the Ethernet segment configuration. The default mode is none and it forces the user to configure a manual ESI. When type-1 is configured, a manual ESI cannot be configured in the ES and the ESI is auto-derived in accordance with the RFC 7432 ESI type 1 definition. An ESI type 1 encodes 0x01 in the ESI type octet (T=0x01) and indicates that IEEE 802.1AX LACP is used between the PEs and CEs.
The ESI is auto-derived from the CE's LACP PDUs by concatenating the following parameters:
CE LACP system MAC address (6 octets)
The CE LACP system MAC address is encoded in the high-order 6 octets of the ESI value field.
CE LACP port key (2 octets)
The CE LACP port key is encoded in the 2 octets next to the system MAC address.
The remaining octet is set to 0x00.
The following usage considerations apply to auto-ESI type 1:
ESI type 1 is only supported on non-virtual Ethernet segments associated with LAGs when LACP is enabled.
Single-active or all-active modes are supported. When used with a single-active node, the CE must be attached to the PEs by a single LAG, which allows the multihomed PEs to auto-derive the same ESI.
Changing the auto-esi command requires an ES shutdown.
When the ES is enabled but the ESI has not yet been auto-derived, no multihoming routes are advertised for the ES. ES and AD routes are advertised only after ESI type 1 is auto-derived and the ES is enabled.
When the ES LAG is operationally down as a result of the ports or LACP going down, the previously auto-derived ESI is retained. Consequently, convergence is not impacted when the LAG comes back up; if the CE's LACP information is changed, the ES goes down and a new auto-derived type 1 ESI is generated.