2Virtualization

• 2.1Device virtualization (hypervisors, VMs, and virtual switching)

  Covers the two forms of the hypervisor that let multiple virtual machines (VMs) share one physical server—type 1 (bare metal) and type 2 (hosted on a host OS)—the virtual NICs and resource allocation a VM uses, and the virtual switching that connects VMs to each other and to the outside, framed as the design and diagnostic judgment of "which form fits this requirement" and "what to suspect when a VM cannot reach the outside."

• 2.2Configuring and verifying data path virtualization (VRF, GRE, and IPsec)

  Covers VRF, which holds multiple independent routing tables inside one router/L3 switch (route separation that tolerates overlapping addresses); GRE, which wraps arbitrary protocols to build a logical link (encapsulation only, no encryption); IPsec, which supplies confidentiality/integrity; and GRE over IPsec, which combines them—all as configuration commands, show-based verification, and the isolation of typical failures.

• 2.3Network virtualization concepts (LISP and VXLAN)

  Covers LISP, which separates an endpoint's identity from its location (resolving through the split between EID and RLOC and a mapping system), and VXLAN, which overlays L2 segments on an L3 network (the VNI is 24 bits, giving about 16 million segments, encapsulated over UDP 4789), together with why SD-Access uses LISP for the control plane and VXLAN for the data plane, from both a conceptual and a fault-isolation standpoint.