Ethernet Virtual Private Network (EVPN) is a next-generation full-service bearer VPN solution. It unifies the control planes for various VPN services and uses BGP extensions to transmit Layer 2 or Layer 3 reachability information, separating the forwarding plane from the control plane.
Lack of support for load balancing: VPLS does not support traffic load balancing in multi-homing networking scenarios.
High network resource usage: Interworking between sites requires all PEs serving these sites on the ISP backbone network to be fully meshed, with PWs established between every two PEs. The amount of network resources consumed for PW establishment increases as the number of PEs increases. Furthermore, a significant number of ARP messages must be transmitted for MAC address learning. These ARP messages not only consume network bandwidth, but may also consume CPU resources on remote sites that do no need to learn the MAC addresses carried in them.
EVPN uses BGP extensions to implement MAC address learning and advertisement on the control plane instead of the data plane. This function allows a device to manage MAC addresses in the same way as it manages routes, implementing load balancing between EVPN routes with the same destination MAC address but different next hops.
EVPN does not require PEs on the ISP backbone network to be fully meshed. This is because PEs on an EVPN communicate using BGP, which provides the route reflection function. As such, a route reflector (RR) can be deployed on the carrier backbone network to reflect EVPN routes to PEs with which the RR has established peer relationships. This significantly reduces network complexity and the number of network signaling messages.
EVPN enables PEs to learn local MAC addresses using ARP and learn remote MAC and IP addresses using MAC/IP advertisement routes. The PEs can then cache these addresses locally. After receiving an ARP request, a PE searches its locally cached MAC and IP address information based on the destination IP address in the ARP request, and then returns an ARP reply when it finds the corresponding information. This reduces consumption of network resources because the PE does not broadcast ARP requests to other PEs.
Improved link utilization and transmission efficiency: EVPN supports load balancing, fully utilizing network resources and alleviating network congestion.
Reduced network resource consumption: By deploying RRs on the public network, EVPN decreases the number of logical connections required between PEs on the public network. In addition, EVPN enables PEs to respond to ARP requests from connected sites using locally cached MAC addresses, minimizing the amount of broadcast ARP requests.