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8.4.1. Constructing Ethernet A-D per EVPN Instance Route

8.4.1. Constructing Ethernet A-D per EVPN Instance Route​

This section describes the procedures used to construct the Ethernet A-D per EVPN instance (EVI) route, which is used for aliasing (as discussed above). Support of this route is OPTIONAL.

The Route Distinguisher (RD) MUST be set per Section 7.9.

The Ethernet Segment Identifier MUST be a 10-octet entity as described in Section 5 ("Ethernet Segment"). The Ethernet A-D route is not needed when the Segment Identifier is set to 0.

The Ethernet Tag ID is the identifier of an Ethernet tag on the Ethernet segment. This value may be a 12-bit VLAN ID, in which case the low-order 12 bits are set to the VLAN ID and the high-order 20 bits are set to 0. Or, it may be another Ethernet tag used by the EVPN. It MAY be set to the default Ethernet tag on the Ethernet segment or to the value 0.

Note that the above allows the Ethernet A-D route to be advertised with one of the following granularities:

  • One Ethernet A-D route per <ESI, Ethernet Tag ID> tuple per MAC-VRF. This is applicable when the PE uses MPLS-based disposition with VID translation or may be applicable when the PE uses MAC-based disposition with VID translation.

  • One Ethernet A-D route for each <ESI> per MAC-VRF (where the Ethernet Tag ID is set to 0). This is applicable when the PE uses MAC-based disposition or MPLS-based disposition without VID translation.

The usage of the MPLS label is described in Section 14 ("Load Balancing of Unicast Packets").

The Next Hop field of the MP_REACH_NLRI attribute of the route MUST be set to the IPv4 or IPv6 address of the advertising PE.

The Ethernet A-D route MUST carry one or more Route Target (RT) attributes, per Section 7.10.

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