In an EVPN-VXLAN fabric, providing a redundant L3 gateway that conserves IP address space is achieved by implementing an anycast gateway. This involves configuring Integrated Routing and Bridging (IRB) interfaces on multiple PE devices with the exact same IP address and the same MAC address. This configuration makes the multiple physical gateways appear as a single logical gateway to the end hosts. Hosts send traffic to this single logical gateway, and the fabric routes it to the nearest physical PE, providing both redundancy and load balancing without consuming additional IP addresses from the subnet.

A. Using different MAC addresses for the same IP on different PEs would cause MAC address flapping on hosts and connected switches, leading to network instability.

B. A Virtual Gateway Address (VGA) is typically associated with VRRP. While VRRP can be used, the native EVPN anycast gateway feature (same IP/MAC) is more efficient and integrated.

D. Using different IP addresses defeats the purpose of conserving address space and providing a single, seamless default gateway to all hosts in the subnet.

1. Juniper Networks TechLibrary. (2023). Default Gateway in an EVPN-VXLAN Overlay Network. "To enable this feature, you configure the same gateway IP address and MAC address on the IRB interfaces of all the leaf devices that you want to participate in providing default gateway services." Retrieved from https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/concept/evpn-vxlan-default-gateway.html

2. Juniper Networks TechLibrary. (2023). Understanding EVPN with VXLAN Data Plane Encapsulation. In the section "Default Gateway," it describes using the same IP and MAC on IRB interfaces across leaf devices for anycast gateway functionality. Retrieved from https://www.juniper.net/documentation/us/en/software/junos/evpn-vxlan/topics/concept/evpn-vxlan-overview.html