4A0-115: Nokia Ethernet Virtual Private Network ServicesDemo

Ethernet A-D per ES routes (EVPN Type 1) carry the ESI Label extended community, which conveys the Ethernet Segment Identifier label used by remote PEs to perform split-horizon filtering, preventing multihomed BUM traffic from looping back onto the originating Ethernet segment. In these routes the Ethernet Tag ID is set to MAX-ET (0xFFFFFFFF) rather than zero, and the MPLS label field itself is not used (set to zero) since the aliasing label is carried instead in the Ethernet A-D per-EVI route. Per-ES routes are primarily used for fast convergence/mass withdrawal and split-horizon (loop prevention), not for advertising general ES service availability, which is the role of the EVPN Type 4 route.