The Cisco Virtual Topology System (VTS) is a standards-based, open, overlay management and provisioning system for data center networks. It automates DC overlay fabric provisioning for both physical and virtual workloads.

Cisco VTS provides a network virtualization architecture and software-defined networking (SDN) framework that meets the requirements of multitenant data centers for cloud services. It enables a policy-based approach for overlay provisioning.

Cisco VTS automates complex network overlay provisioning and management tasks through integration with cloud orchestration systems such as OpenStack and VMware vCenter and abstracts out the complexity involved in managing heterogeneous network environments. The solution can be managed from the embedded Cisco VTS GUI or entirely by a set of northbound Representational State Transfer (REST) APIs that can be consumed by orchestration and cloud management systems.

Cisco VTS provides:

• Fabric automation

• Programmability

• Open, scalable, standards based solution

• Cisco Nexus 5000, 7000, and 9000 Series Switches. For more information, see Supported Platforms in Cisco VTS 2.1.5 Installation Guide.

• Software forwarder (Virtual Topology Forwarder [VTF])

Cisco VTS architecture has two main components: the Policy Plane and the Control Plane. These perform core functions such as SDN control, resource allocation, and core management function.

Figure 1. Cisco VTS Architecture

• Policy Plane: The policy plane enables Cisco VTS to implement a declarative policy model designed to capture user intent and render it into specific device-level constructs. The solution exposes a set of modular policy constructs that can be flexibly organized into user-defined services for use cases across service provider and cloud environments. These policy constructs are exposed through a set of REST APIs that can be consumed by orchestrators and applications to express user intent, or instantiated through the Cisco VTS GUI. Policy models are exposed as system policies or service policies.

  System policies allow administrators to logically group devices into pods within or across data centers to define Admin Domains with common system parameters (for example, BGP-EVPN control plane with distributed Layer 2 and 3 gateways).

  The inventory module maintains a database of the available physical entities (for example, data center interconnect [DCI] routers and top-of-rack leaf, spine, and border-leaf switches) and virtual entities (for example, VTFs) in the Virtual Topology System domain. The database also includes interconnections between these entities and details about all services instantiated within a Virtual Topology System domain.

  The resource management module manages all available resource pools in the Virtual Topology System domain, including VLANs, VXLAN Network Identifiers (VNIs), IP addresses, and multicast groups.

• Control Plane: The control plane module serves as the SDN control subsystem that programs the various data planes including the VTFs residing on the x86 servers, hardware leafs, DCI gateways. The control plane hosts the Cisco IOS XRv Software instance that provides route peering capabilities between the DCI gateways or to a BGP route reflector. Cisco IOS XRv is the virtualized version of Cisco IOS XR Software. The control plane enables an MP-BGP EVPN-based control plane for VXLAN overlays originating from leafs or software VXLAN tunnel endpoints (VTEPs).

  The device management module enables device configuration and management capabilities within Virtual Topology System, with multiprotocol support to support a multivendor environment.

Cisco VTS solution provides a l2/l3 software switch that can act as a software VTEP and is called Virtual Topology forwarder (VTF). Cisco VTS can be deployed with a Virtual Topology Forwarder (VTF). VTF is a lightweight, multitenant software data plane designed for high performance packet processing on x86 servers. VTF uses Vector Packet Processing (VPP). VPP is a full-featured networking stack with a software forwarding engine. VTF leverages VPP technology and Intel Data Path Development Kit (DPDK) for high performance Layer 2 (L2), Layer 3 (L3), and VXLAN packet forwarding.

VTF allows Cisco VTS to terminate VXLAN tunnels on host servers by using the VTF as a Software VXLAN Tunnel Endpoint (VTEP). Cisco VTS also supports hybrid overlays by stitching together physical and virtual endpoints into a single VXLAN segment.

VTF is deployed as a virtual machine to deliver a high-performance software data plane on a host server.

The Virtual Topology System solution is designed to support redundancy, with two solution instances running on separate hosts in an active-standby configuration.

During initial setup, each instance is configured with both an underlay IP address and a virtual IP address. Virtual Router Redundancy Protocol (VRRP) is used between the instances to determine which instance is active.

The active-instance data is synchronized with the standby instance after each transaction to help ensure consistency of the control-plane information to accelerate failover after a failure. BGP peering is established from both Virtual Topology System instances for the distribution of tenant-specific routes. During the switchover, nonstop forwarding (NSF) and graceful restart help ensure that services are not disrupted.

See the Configuring High Availability section of the Cisco VTS 2.1.5 Installation Guide for the detailed procedure about setting up high availability.