If SNMP discovery fails or is not supported by a Cisco, Huawei, or Juniper M/T device, or if additional information is needed for a device, the drivers invoke CLI commands to query the device for MPLS, VPN, BGP, and relationship information.
To discover MPLS information for Huawei devices, or to discover MPLS, L2VPN, and L3VPN information for Juniper ERX devices, the drivers invoke CLI commands exclusively to gather the required information.
One CLI discovery session is started for each device. Appendix B, “CLI Commands Invoked for Discovery and LSP Ping,” provides a description of the commands that are invoked by a CLI discovery session.
A CLI discovery session uses the appropriate CLI device-access object to access a device through the Telnet, SSH1, or SSH2 protocol. The session uses the “site key” to decrypt a copy of the user password in the CLI device-access object just before the session attempts to access the device. As explained in the System Administration Guide, the site key is created during the installation of applications.
If the probing of a device is successful, the MPLS Topology Server creates an object for each discovered MPLS, VPN, or BGP component and places the objects in its repository. If the probing is not successful, the MPLS Topology Server places the name of the probed device on the Pending Elements list. Chapter 9, “Understanding Discovery Results,” provides information about discovery errors and the Pending Elements list.
