Understanding the Session Protocol in Automation Scripts

SLAX and XSLT scripts can use the jcs:open() function to establish a connection with a Junos device. The function includes an option to establish a session with either the Junos XML protocol server on a Junos device or the NETCONF server on devices that have the NETCONF service over SSH enabled.

The Junos XML management protocol is a Juniper Networks proprietary protocol that you use to request information from and configure Junos devices. The NETCONF XML management protocol is a standard that you use to request or change the configuration on network devices. The following RFCs define the NETCONF protocol:

• RFC 6241, NETCONF Configuration Protocol

• RFC 6242, Using the NETCONF Configuration Protocol over Secure SHell (SSH)

The jcs:open() function supports the following session protocol types:

• junoscript—(Default) Session with the Junos XML protocol server on a Junos device. This session type supports the operations defined in the Junos XML protocol and the Junos XML API. You can use the protocol operations and Junos XML API content to configure the device or request information about the device configuration or operation.

• netconf—Session with the NETCONF XML protocol server on a network device over an SSHv2 connection. The device must have NETCONF over SSH enabled.

• junos-netconf—Proprietary session with the NETCONF XML protocol server over an SSHv2 connection on a Junos device.

On Junos devices, the NETCONF server has the additional capabilities defined in http://xml.juniper.net/netconf/junos/1.0. On these devices, the NETCONF server supports NETCONF XML protocol operations, most Junos XML protocol operations, and the tag elements defined in the Junos XML API. For netconf and junos-netconf sessions, you should use only native NETCONF operations and the extensions available in the Junos XML protocol for configuration operations as documented in the NETCONF XML Management Protocol Developer Guide.

To call the jcs:open() function and specify the session protocol, use the following syntax:

SLAX Syntax

XSLT Syntax

The session-options parameter is an XML node-set that specifies the session type and connection parameters. The session type is one of the session values: junoscript, netconf, or junos-netconf. The format of the node-set is:

If you do not specify a username and it is required for the connection, the script uses the local name of the user executing the script. The <passphrase> and <password> elements serve the same purpose. If you do not specify a passphrase or password element and it is required for authentication, the device to which you are connecting should prompt you for one during script execution.

Devices running Junos OS Evolved support only password-less login when establishing a local or remote connection using the jcs:open() function. Junos OS Evolved does not support using an interactive password or supplying a password as a function argument. To effect a local or remote connection, execute this functionality by way of a password-less login or else the script could encounter authentication issues.

Optionally, you can specify the server port number for netconf and junos-netconf sessions. If you do not specify a port number, jcs:open() connects to the NETCONF server using the default port 830. Specifying a port number has no impact on junoscript sessions, which always use SSH port 22.

To redirect the SSH connection to originate from within a specific routing instance, include either the instance or routing-instance element and specify the routing instance name. The routing instance must be configured at the [edit routing-instances] hierarchy level. The remote device must be reachable either using the routing table for that routing instance or from one of the interfaces configured under that routing instance.

To verify the protocol for a specific connection, call the jcs:get-protocol(connection) extension function and pass the connection handle as the argument. The function returns “junoscript”, “netconf”, or “junos-netconf”, depending on the session type.

During session establishment with a NETCONF server, the client application and NETCONF server each emit a <hello> element. The <hello> contents specify which operations, or capabilities, the device supports from among those defined in the NETCONF specification or published as proprietary extensions. In netconf and junos-netconf sessions, you can retrieve the session capabilities of the NETCONF server by calling the jcs:get-hello(connection) extension function.

For example, the NETCONF server on a typical device running Junos OS might return the following capabilities: