Aliasing and Backup Paths

Aliasing and backup paths are important for BGP EVPN multihoming. With aliasing, a remote Provider Edge (PE) device can utilize all multihomed PE devices as the next-hop for a Customer Edge (CE) device, even if it has learned the CE Media Access Control (MAC) address from only one of those PE devices. This is possible because multihomed PE devices can signal reachability to that MAC address's Ethernet Virtual Private Network (VPN) Instance (EVI) or Ethernet Segment (ES) via Ethernet VPN (EVPN) routes. Aliasing ensures that multiple paths to a destination are utilized effectively, providing redundancy.

Backup Path is a closely related functionality applicable in single-active redundancy mode. Aliasing and Backup Path functionality can also be utilized by singlehomed PE devices that do not support all multihoming features.