Virtual Hub-and-Spoke in BGP EVPNs

Ethernet Virtual Private Network (EVPN) solution is becoming pervasive for Network Virtualization Overlay (NVO) services in data center (DC) applications and as the next generation virtual private LAN services in service provider (SP) applications. The use of host IP default route and host unknown MAC route within a DC is well understood in order to ensure that leaf nodes within a DC only learn and store host MAC and IP addresses for that DC. All other host MAC and IP addresses from remote DCs are learned and stored in DC GW nodes thus alleviating leaf nodes from learning host MAC and IP addresses from the remote DCs. This draft further optimizes the MAC and IP address learning at the leaf nodes such that a leaf node within a DC only needs to learn and store MAC and IP addresses associated with the sites directly connected to it. A leaf node does not need to learn and store MAC and IP addresses from any other leaf nodes thus reducing the number of learned MACs and IP addresses per EVI substantially. The modifications provided by this draft updates and extends RFC7024 for BGP EVPN Address Family.