In an EVPN operation, how does the PE determine and advertise Ethernet segment reachability?

In an EVPN operation, the PE (Provider Edge) router determines and advertises Ethernet segment reachability by discovering remote ESIs (Ethernet Segment Identifiers) and determining their redundancy mode (all-active or single-active). This is crucial in multihoming scenarios where the PE needs to auto-discover remote PEs and the corresponding redundancy mode. In case of segment failures, PEs withdraw the routes used at this stage to trigger fast convergence by signaling a MAC mass withdrawal on remote PEs3.

References:

Cisco, “EVPN Configuration Guide for Cisco 8000 Series Routers, IOS XR Release 7.11.x”

Huawei, “Overview of EVPN - New IP Technologies”