The Cisco Networking Services Frame Relay Zero Touch feature provides a Cisco Networking Services zero touch deployment solution over Frame Relay where the CPE router discovers its data-link connection identifier (DLCI) and IP address dynamically, and then contacts a Cisco Networking Services engine to retrieve its full configuration automatically. This capability is made possible through a single generic bootstrap configuration file common across all service provider end customers subscribing to the services. Within the Cisco Networking Services framework, customers who deploy Frame Relay can create this generic bootstrap configuration without device-specific or network-specific information such as the DLCI, IP address, interface type, controller type (if applicable), or the next hop interface used for the static default route.
The following image illustrates a typical customer network architecture using Frame Relay.
Figure 1. Connectivity in a Frame Relay Customer Network
The CPE router is deployed at multiple sites. Each site connects to a Frame Relay cloud through a point-to-point permanent virtual circuit (PVC). Connectivity from the Frame Relay cloud to the corporate office is through a PVC that terminates at the corporate office. IP traffic sent to the Cisco Networking Services configuration engine is routed through the corporate office. The PVC is identified by its DLCI. The DLCI can vary between branch offices. In order to support zero touch deployment, the CPE router must be able to learn which DLCI to use to connect to the Cisco Networking Services configuration engine.
To support the zero touch capability, the Frame Relay functionality has been modified in the following two ways:
- A new Cisco IOS command, the
dynamiccommand has been introduced to discover the CPE router’s IP address dynamically based on the aggregator router’s IP address. To configure IP over Frame Relay, the local IP address must be configured on the interface.
- The CPE router can now read Local Management Interface (LMI) messages from a Frame Relay switch and determine the list of available DLCIs.
The Cisco Networking Services connect functionality is configured with a set of Cisco Networking Services connect templates. A Cisco Networking Services connect profile is created for connecting to the Cisco Networking Services configuration engine and to implement the Cisco Networking Services connect templates on a CPE router. Cisco Networking Services connect variables can be used as placeholders within a Cisco Networking Services connect template configuration. These variables, such as the active DLCI, are substituted with real values before the Cisco Networking Services connect templates are sent to the router’s parser.
When a CPE router is placed in a Frame Relay network, it contains a generic bootstrap configuration. This configuration includes customer-specific Frame Relay configuration (including the LMI type), Cisco Networking Services connect templates, Cisco Networking Services connect profiles, and the
initial command. This command initiates the Cisco Networking Services connect function.
The Cisco Networking Services connect functionality begins by selecting the first available controller or interface specified by the Cisco Networking Services connect profile and then performs multiple ping iterations through all the associated active DLCIs. For each iteration, the Cisco Networking Services connect function attempts to ping the Cisco Networking Services configuration engine. If the ping is successful, the pertinent configuration information can be downloaded from the Cisco Networking Services configuration engine.
When iterating over the active DLCIs on a Frame Relay interface, the router must be able to automatically go through a list of active DLCIs returned by the LMI messages for that interface and select an active DLCI to use. When more than one of the active DLCIs allow IP connectivity to the Cisco Networking Services configuration engine, the DLCI used will be the first one tried by the Cisco Networking Services connect functionality. If the ping attempt is unsuccessful, the next active DLCI is tried and so on. If connectivity to the Cisco Networking Services configuration engine is unsuccessful for all active DLCIs, the Cisco Networking Services connect function removes the configuration applied to the selected controller or interface, and the Cisco Networking Services connect process restarts with the next available controller or interface specified by the Cisco Networking Services connect profile.
The Cisco Networking Services Frame Relay Zero Touch feature provides the following benefits:
- A service provider can have a single common bootstrap configuration.
- The generic bootstrap configuration does not require the IP address to be hard-wired.
- The point-to-point DLCI does not need to be known in advance.
- IP directly over Frame Relay is allowed.
- Use of a channel service unit (E1 or T1 controller) is allowed.