ec- tive of the access node. EVPN with its point-to-point virtual psuedowire service, flexible cross connect bundling, and multihomed attachment support is ideal for meeting these access connectivity requirements across wide area core networks as well as metro and regional networks as shown in Figures 12.7 and 12.8. In Figure 12.8, A- denotes access connected to the leaf, C- denotes compute server con- nected to the leaf, P- denotes provider core connected to the leaf in the terms A-Leaf, C-Leaf, and P-Leaf. Out-of-region cluster Metro cluster Connections or virtual tunnels Virtual ports Physical ports A cluster is a set of geolocated AIC zones that provide resiliency by allowing virtual functions to migrate or failover FIGURE 12.7 Metro clusters. Building the Network of the Future EVPN Tunnel Ethernet UNI/VLAN (Server) EVPN tunnel end point (ETEP) C, A, P, S C-Leaf, A-Leaf, P-Leaf, Spine Whiteboxes Network Fabric (Data Center/CO) Network Fabric (Data Center/ (Server) (Server) FIGURE 12.8 Interconnectivity provided by EVPN. 12.5.2 CLOUD OVERLAY CONNECTIVITY Connectivity among edge service VNFs and cloud virtual routers requires a combination of layer 2 and layer 3 VNFs. VNFs on the same subnet require layer 2 Ethernet multipoint bridging. Or, they may only require a virtual IP network providing a default gateway and IP layer 3 routing. Then, many will require both, with a virtual network that does integrated intra-subnet bridging and default gateway IP routing (sometimes called integrated routing and bridging). And the resiliency requirement is that these VNFs see connectivity on their hosts via an NIC bond for redundancy, while the bond is actually a multichassis link aggregation group (LAG) across a pair of neighbor leaf switches. EVPN meets the layer 2 and layer 3 virtual routing requirements and provides a standardized approach to support multichassis LAG redundancy. 12.5.3 EVPN EVPN is a multiservice MPLS technology for both Ethernet point-to-point, multipoint, and IP rout- ing virtual networks. It has virtu