Connect to the Junos XML Protocol Server Using Perl Client Applications

The Junos XML protocol server supports several access protocols. For each connection to the Junos XML protocol server on a device running Junos OS, the application must specify the protocol it is using. Using SSH or Secure Sockets Layer (SSL) is recommended because they provide greater security by encrypting all information before transmission across the network.

Before your application can run, you must satisfy the prerequisites for the access protocol it uses. For some protocols this involves activating configuration statements on the device, creating encryption keys, or installing additional software on the device running Junos OS or the machine where the application runs. For instructions, see Satisfying the Prerequisites for Establishing a Connection to the Junos XML Protocol Server.

Establishing a connection to the Junos XML protocol server on a device running Junos OS is one of the more time-intensive and resource-intensive functions performed by an application. If the application sends multiple requests to a routing platform, it makes sense to send all of them within the context of one connection. If your application sends the same requests to multiple devices, you can structure the script to iterate through either the set of devices or the set of requests. Keep in mind, however, that your application can effectively send only one request to one Junos XML protocol server at a time. This is because the JUNOS::Device object does not return control to the application until it receives the closing </rpc-reply> tag that represents the end of the Junos XML protocol server’s response to the current request.

The JUNOS::Device object takes the following parameters, specified as keys in a Perl hash:

• access—(Required) The access protocol to use when communicating with the Junos XML protocol server. Acceptable values are "telnet", "ssh", "clear-text", and "ssl". Before the application runs, satisfy any protocol-specific prerequisites.

• hostname—(Required) The name of the device to which to connect. For best results, specify either a fully qualified hostname or an IP address.

• login—(Required) The username under which to establish the connection to the Junos XML protocol server and issue requests. The username must already exist on the specified device and have the permission bits necessary for making the requests invoked by the application.

• password—(Required) The password corresponding to the username.

• junos_key—(Optional) When requesting configuration data using the get_configuration() method, set the value of the parameter to 1 to include the junos:key="key" attribute in the output of XML-formatted configuration data. The default value of the parameter is 0. The junos:key="key" attribute indicates that a child configuration tag element is the identifier for its parent tag element. The attribute does not appear in formatted ASCII output.

The sample scripts record the parameters in a Perl hash called %deviceinfo, declared as follows:

The sample scripts included in the Junos XML Protocol Perl client distribution obtain the parameters from options entered on the command line by a user. For more information about collecting parameter values interactively, see Collecting Parameters Interactively in Junos XML Protocol Perl Client Applications. Your application can also obtain values for the parameters from a file or database, or you can hardcode one or more of the parameters into the application code if they are constant.

In addition to the parameters required by the JUNOS::Device object, applications might need to define other parameters, such as the name of the file to which to write the data returned by the Junos XML protocol server in response to a request, or the name of the Extensible Stylesheet Transformation Language (XSLT) file to use for transforming the data.

As with the parameters required by the JUNOS::Device object, the client application can hardcode the values in the application code, obtain them from a file, or obtain them interactively. The sample scripts obtain values for these parameters from command-line options in the same manner as they obtain the parameters required by the JUNOS::Device object (discussed in Obtaining and Recording Parameters Required by the JUNOS::Device Object). Several examples follow.

The following line enables a debugging trace if the user includes the -d command-line option. It invokes the JUNOS::Trace::init routine defined in the JUNOS::Trace module, which is imported with the JUNOS::Device object.

The following line sets the $outputfile variable to the value specified by the -o command-line option. It names the local file to which the Junos XML protocol server’s response is written. If the -o option is not provided, the variable is set to the empty string.

The following code from the diagnose_bgp.pl script defines which XSLT file to use to transform the Junos XML protocol server’s response. The first line sets the $xslfile variable to the value specified by the -x command-line option. If the option is not provided, the script uses the text.xsl file supplied with the script, which transforms the data to ASCII text. The if statement verifies that the specified XSLT file exists; the script terminates if it does not.

The following code from the load_configuration.pl script defines whether to merge, replace, update, or overwrite the new configuration data into the configuration database. The first two lines set the $load_action variable to the value of the -a command-line option, or to the default value merge if the option is not provided. If the specified value does not match one of the valid actions defined by the VALID_ACTIONS constant, the script invokes the output_usage subroutine to print the usage message.

After obtaining values for the parameters required for the JUNOS::Device object, each sample script records them in the %deviceinfo hash.

The script then invokes the Junos XML protocol-specific new subroutine to create a JUNOS::Device object and establish a connection to the specified routing, switching, or security platform. If the connection attempt fails (as tested by the ref operator), the script exits.