(Rekhter, 2007) are widely used layer-2 virtual network services for large campuses or multilocation wide area networks (Anderson, 2006). VPWS defines point-to-point services and VPLS defines multipoint services. Ethernet VPN (EVPN) (Sajassi, 2015) is the newest standard for building and delivering CUG services for Ethernet end points. IP routing defines a set of protocols that compute the path that a data packet follows in order to travel across multiple networks from the packet's source to its destination. Data are routed from its source to its destination through a series of routers, and often across multiple networks. The IP-routing protocols enable routers to build a forwarding table that correlates destinations with next hop addresses. In basic IP routing, all sources and destinations are visible to each other by means of routing protocols. In order to create CUGs over IP networks, we need to use an approach that is commonly referred to as overlay networks. An overlay network is a virtual network implemented over an underlying IP Network Functions Virtualization CUG 1 VLAN-32 (broadcast domain A) User-1 User-2 User-3 User-4 Switch-1 Switch-2 User-5 User-6 User-7 User-8 CUG 2 VLAN-44 (Broadcast domain B) FIGURE 3.1 Simple Ethernet virtual networks using VLANs. CUG-1 Router-1 Router-2 CUG-1 IP Tunnels Underlay IP Network CUG-2 Router-3 Router-4 CUG-2 FIGURE 3.2 Virtual network connections using IP tunneling. VRF 2 VRF 1 Global Routing Table Router FIGURE 3.3 Virtualization of IP networks using VRFs. network. There are two widely used technologies for creating overlay IP networks: IP tunnels and virtual route forwarding (VRF). IP tunnels (Simpson, 1995) are used for connecting two virtual IP end points that do not have a routing path to each other (see Figure 3.2). The tunnel uses a routing protocol across a common intermediate IP transport network. The IP tunnel is a virtual overlay network connection between the end points and the common intermediate transport network, which is sometimes referred to as the u