CNS is a foundation technology for linking users to networking services and provides the infrastructure for the automated configuration of large numbers of network devices. Many IP networks are complex with many devices, and each device must currently be configured individually. When standard configurations do not exist or have been modified, the time involved in initial installation and subsequent upgrading is considerable. The volume of smaller, more standardized, customer networks is also growing faster than the number of available network engineers. Internet service providers (ISPs) now need a method for sending out partial configurations to introduce new services. To address all these issues, CNS has been designed to provide "plug-and-play" network services using a central directory service and distributed agents. CNS features include CNS configuration and event agents and a Flow-Through Provisioning structure. The configuration and event agents use a CNS configuration engine to provide methods for automating initial Cisco IOS XE device configurations, incremental configurations, and synchronized configuration updates, and the configuration engine reports the status of the configuration load as an event to which a network monitoring or workflow application can subscribe. The CNS Flow-Through Provisioning uses the CNS configuration and event agents to provide an automated workflow, eliminating the need for an on-site technician.

The CNS configuration agent is involved in the initial configuration and subsequent partial configurations on a Cisco IOS XE device. To activate the CNS configuration agent, enter any of the cns config CLI commands.

When a routing device first comes up, it connects to the configuration server component of the CNS configuration agent by establishing a TCP connection through the use of the cns config initial command, a standard CLI command. The device issues a request and identifies itself by providing a unique configuration ID to the configuration server.

When the CNS web server receives a request for a configuration file, it invokes the Java servlet and executes the corresponding embedded code. The embedded code directs the CNS web server to access the directory server and file system to read the configuration reference for this device (configuration ID) and template. The Configuration Agent prepares an instantiated configuration file by substituting all the parameter values specified in the template with valid values for this device. The configuration server forwards the configuration file to the CNS web server for transmission to the routing device.

The CNS configuration agent accepts the configuration file from the CNS web server, performs XML parsing, checks syntax (optional), and loads the configuration file. The routing device reports the status of the configuration load as an event to which a network monitoring or workflow application can subscribe.

For more details on using the Cisco CNS configuration engine to automatically install the initial CNS configuration, see the Cisco CNS Configuration Engine Administrator's Guide at http://www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/cns/ce/rel13/ag13/index.htm .

Once the network is up and running, new services can be added using the CNS configuration agent. Incremental (partial) configurations can be sent to routing devices. The actual configuration can be sent as an event payload by way of the event gateway (push operation) or as a signal event that triggers the device to initiate a pull operation.

The routing device can check the syntax of the configuration before applying it. If the syntax is correct, the routing device applies the incremental configuration and publishes an event that signals success to the configuration server. If the device fails to apply the incremental configuration, it publishes an event that indicates an error.

Once the routing device has applied the incremental configuration, it can write the configuration to NVRAM or wait until signaled to do so.

When a routing device receives a configuration, the device has the option to defer application of the configuration upon receipt of a write-signal event. The CNS Configuration Agent feature allows the device configuration to be synchronized with other dependent network activities.

The Cisco Networking Services (CNS) Config Retrieve Enhancement with Retry and Interval feature adds new functionality to the cns config retrieve command enabling you to specify the retry interval and an amount of time in seconds to wait before attempting to retrieve a configuration from a trusted server.

The CNS Interactive CLI feature provides a XML interface that allows you to send interactive commands to a router, such as commands that generate prompts for user input. A benefit of this feature is that interactive commands can be aborted before they have been fully processed. For example, for commands that generate a significant amount of output, the XML interface can be customized to limit the size of the output or the length of time allowed for the output to accumulate. The capability to use a programmable interface to abort a command before its normal termination (similar to manually aborting a command) can greatly increase the efficiency of diagnostic applications that might use this functionality. The new XML interface also allows for multiple commands to be processed in a single session. The response for each command is packaged together and sent in a single response event.

The CNS ID is a text string that is used exclusively with a particular CNS agent. The CNS ID is used by the CNS agent to identify itself to the server application with which it communicates. For example, the CNS configuration agent will include the configuration ID when communicating between the networking device and the configuration server. The configuration server uses the CNS configuration ID as a key to locate the attribute containing the Cisco IOS XE CLI configuration intended for the device that originated the configuration pull.

The network administrator must ensure a match between the CNS agent ID as defined on the routing device and the CNS agent ID contained in the directory attribute that corresponds to the configuration intended for the routing device. Within the routing device, the default value of the CNS agent ID is always set to the hostname. If the hostname changes, the CNS agent ID also changes. If the CNS agent ID is set using the CLI, any change will be followed by a message sent to syslog or an event message will be sent.

The CNS agent ID does not address security issues.

The CNS password is used to authenticate the CNS device. You must configure the CNS password the first time a router is deployed, and the CNS password must be the same as the bootstrap password set on the Configuration Engine (CE). If both the router and the CE bootstrap password use their default settings, a newly deployed router will be able to connect to the CE.

Once connected, the CE manages the CNS password. Network administrators must ensure not to change the CNS password. If the CNS password is changed, connectivity to the CE will be lost.

The Command Scheduler (KRON) Policy for System Startup feature enables support for the Command Scheduler upon system startup.

The Command Scheduler allows customers to schedule fully-qualified EXEC mode CLI commands to run once, at specified intervals, at specified calendar dates and times, or upon system startup. Originally designed to work with CNS commands, Command Scheduler now has a broader application. Using the CNS image agent feature, remote routers residing outside a firewall or using Network Address Translation (NAT) addresses can use Command Scheduler to launch CLI at intervals, to update the image running in the router.

Command Scheduler has two basic processes. A policy list is configured containing lines of fully-qualified EXEC CLI commands to be run at the same time or same interval. One or more policy lists are then scheduled to run after a specified interval of time, at a specified calendar date and time, or upon system startup. Each scheduled occurrence can be set to run either once only or on a recurring basis.

The CNS Zero Touch feature provides a zero touch deployment solution where the router contacts a CNS configuration 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 CNS framework, customers can create this generic bootstrap configuration without device-specific or network-specific information such as interface type, line type, or controller type (if applicable).

The CNS connect functionality is configured with a set of CNS connect templates. A CNS connect profile is created for connecting to the CNS configuration engine and to implement the CNS connect templates on a Customer Premise Equipment (CPE) router. CNS connect variables can be used as placeholders within a CNS connect template configuration. These variables, such as the active DLCI, are substituted with real values before the CNS connect templates are sent to the router's parser.

To use the zero touch functionality, the router that is to be initialized must have a generic bootstrap configuration. This configuration includes CNS connect templates, CNS connect profiles, and the cns config initial command. This command initiates the CNS connect function.

The CNS connect functionality performs multiple ping iterations through the router's interfaces and lines, as well as any available controllers. For each iteration, the CNS connect function attempts to ping the CNS configuration engine. If the ping is successful, the pertinent configuration information can be downloaded from the CNS configuration engine. If connectivity to the CNS configuration engine is unsuccessful, the CNS connect function removes the configuration applied to the selected interface, and the CNS connect process restarts with the next available interface specified by the CNS connect profile.

The CNS Zero Touch feature provides the following benefits:

• Ensures consistent CNS commands.
• Use of a channel service unit (E1 or T1 controller) is allowed.

Perform this task to manually install an initial CNS configuration.

Your remote router arrives from the factory with a bootstrap configuration. Upon initial power-on, the router automatically pulls a full initial configuration from the CNS configuration engine, although you can optionally arrange for this manually as well. After initial configuration, you can optionally arrange for periodic incremental (partial) configurations for synchronization purposes.

For more details on using the Cisco CNS configuration engine to automatically install the initial CNS configuration, see the Cisco CNS Configuration Engine Administrator's Guide at http://www.cisco.com/en/US/docs/net_mgmt/configuration_engine/1.3/administration/guide/ag13.html

• Initial CNS Configuration
  
• Incremental Configuration
  

Perform this task to configure CNS security features.

• CNS Trusted Servers
  

Perform this task to set up Command Scheduler policy lists of EXEC CNS commands and configure a Command Scheduler occurrence to specify the time or interval after which the CNS commands will run.

• Command Scheduler Policy Lists
  
• Command Scheduler Occurrences
  
• Examples
  
• Troubleshooting Tips
  

1.    enable

2.    configure terminal

3.    cns mib-access encapsulation {snmp | xml[size bytes]}

4.    cns notifications encapsulation {snmp | xml}

5.    cns inventory

6.    transport event

7.    exit