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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 5 Configuring Cisco IOS CNS Agents
Understanding Cisco Configuration Engine Software
The Configuration Service uses the CNS Event Service to send and receive configuration change events
and to send success and failure notifications.
The configuration server is a web server that uses configuration templates and the device-specific
configuration information stored in the embedded (standalone mode) or remote (server mode) directory.
Configuration templates are text files containing static configuration information in the form of CLI
commands. In the templates, variables are specified using lightweight directory access protocol (LDAP)
URLs that reference the device-specific configuration information stored in a directory.
The Cisco IOS agent can perform a syntax check on received configuration files and publish events to
show the success or failure of the syntax check. The configuration agent can either apply configurations
immediately or delay the application until receipt of a synchronization event from the configuration
server.
Event Service
The Cisco Configuration Engine uses the Event Service for receipt and generation of configuration
events. The event agent is on the switch and facilitates the communication between the switch and the
event gateway on the Configuration Engine.
The Event Service is a highly capable publish-and-subscribe communication method. The Event Service
uses subject-based addressing to send messages to their destinations. Subject-based addressing
conventions define a simple, uniform namespace for messages and their destinations.
NameSpace Mapper
The Configuration Engine includes the NameSpace Mapper (NSM) that provides a lookup service for
managing logical groups of devices based on application, device or group ID, and event.
Cisco IOS devices recognize only event subject-names that match those configured in Cisco IOS
software; for example, cisco.cns.config.load. You can use the namespace mapping service to designate
events by using any desired naming convention. When you have populated your data store with your
subject names, NSM changes your event subject-name strings to those known by Cisco IOS.
For a subscriber, when given a unique device ID and event, the namespace mapping service returns a set
of events to which to subscribe. Similarly, for a publisher, when given a unique group ID, device ID, and
event, the mapping service returns a set of events on which to publish.
What You Should Know About the CNS IDs and Device Hostnames
The Cisco Configuration Engine assumes that a unique identifier is associated with each configured
switch. This unique identifier can take on multiple synonyms, where each synonym is unique within a
particular namespace. The event service uses namespace content for subject-based addressing of
messages.
The Configuration Engine intersects two namespaces, one for the event bus and the other for the
configuration server. Within the scope of the configuration server namespace, the term ConfigID is the
unique identifier for a device. Within the scope of the event bus namespace, the term DeviceID is the
CNS unique identifier for a device.
Because the Configuration Engine uses both the event bus and the configuration server to provide
configurations to devices, you must define both ConfigID and Device ID for each configured switch.