Understanding How Cisco VMS Service Extensions Work
VMS service extensions simplifies how configuration snippets can be applied to a service or a device. VMS leverages the underlying capability of Cisco Network Services Orchestrator (NSO) custom templates, which get pushed along with the derived configuration templates. Service extensions can be used, in most cases, to map services to device configurations, without the need for any additional programming.
VMS service extension templates use variables to map service attributes to the corresponding device configurations and are applied. The service extensions allow a declarative way to describe such manipulations. The VMS operator can apply a service extension template to an existing service chain in VMS or to a device, without having to manually go into the NSO CLI. This service extension template is used by NSO to add, modify, or delete service configuration snippets before NSO pushes the configuration to the devices.
You can apply VMS service extension templates to a service ordering workflow or a single device. When you import a service extension template into VMS, you can specify if the template is to be applied to a service workflow or a device.
When a service extension template is applied to service ordering workflow, VMS service workflow gathers the parameter values the tenant users enter during service ordering process. These values are passed to NSO, which further uses these values in the device configurations.
The following illustration depicts the end-to-end workflow that needs to be followed to work with service extension templates in VMS.
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