Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
Cisco recommends Multiprotocol Label Switching (MPLS) as a network virtualization technique for any-to- any connectivity in large networks. MPLS is typically implemented in an end-to-end fashion at the network edge and requires the edge and core devices to be MPLS-capable. MPLS can support thousands of virtual networks (VNETs) over a full-mesh topology to provide any-to-any connectivity without requiring excessive operational complexity or management resources. Although MPLS is best suited for large networks, integrating MPLS into an existing design and infrastructure can be disruptive, particularly if MPLS- incapable devices must be replaced with MPLS-capable devices at the network edge or in the core.
The Multi-virtual routing and forwarding (Multi-VRF) network virtualization technique, which Cisco also refers to as VRF-Lite, is best suited for small or medium networks. Multi-VRF uses virtual routing and forwarding (VRF) instances to segregate a Layer 3 network. Multi-VRF is typically used to support one-to- one, end-to-end connections; however, Multicast Generic Routing Encapsulation (mGRE) tunnels could be used to create any-to-any connectivity in small networks. Cisco considers a full mesh of mGRE tunnels in larger networks impractical because of the increased operational complexity and management load. On Cisco platforms, Multi-VRF network virtualization supports up to eight VNETs before operational complexity and management become problematic. The VNETs created by Multi-VRF mirror the physical infrastructure upon which they are built, and most Cisco platforms support Multi-VRF; therefore, the general network design and overall infrastructure do not require disruptive changes in order to support a Multi-VRF overlay topology.
Newer Cisco platforms support Easy Virtual Networking (EVN), which is a network virtualization that also uses VRFs to segregate Layer 3 networks. EVN supports up to 32 VNETs before operational complexity and management become problematic. Cisco recommends using EVN instead of Multi-VRF in small and medium networks. Although EVN is backward-compatible with Multi-VRF, implementing a homogeneous EVN topology would require replacing unsupported hardware with EVN-capable devices. Replacing infrastructure is typically disruptive and may require additional modifications to the existing network design.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 4, VRF, p. 154
Cisco: Borderless Campus Network Virtualization-Path Isolation Design Fundamentals: Path Isolation