4-6
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter4 Configuring Cisco IOS Configuration Engine
Configuring Cisco IOS Agents

Incremental (Partial) Configuration

After the network is running, new services can be added by using the Cisco IOS agent. Incremental
(partial) configurations can be sent to the switch. 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 switch to
initiate a pull operation.
The switch can check the syntax of the configuration before applying it. If the syntax is correct, the
switch applies the incremental configuration and publishes an event that signals success to the
configuration server. If the switch does not apply the incremental configuration, it publishes an event
showing an error status. When the switch has applied the incremental configuration, it can write it to
NVRAM or wait until signaled to do so.

Synchronized Configuration

When the switch receives a configuration, it can defer application of the configuration upon receipt of a
write-signal event. The write-signal event tells the switch not to save the updated configuration into its
NVRAM. The switch uses the updated configuration as its running configuration. This ensures that the
switch configuration is synchronized with other network activities before saving the configuration in
NVRAM for use at the next reboot.
Configuring Cisco IOS Agents
The Cisco IOS agents embedded in the switch Cisco IOS software allow the switch to be connected and
automatically configured as described in the “Enabling Automated CNS Configuration” section on
page 4-6. If you want to change the configuration or install a custom configuration, see these sections
for instructions:
•Enabling the CNS Event Agent, page 4-7
•Enabling the Cisco IOS CNS Agent, page 4-9

Enabling Automated CNS Configuration

To enable automated CNS configuration of the switch, you must first complete the prerequisites in
Table 4 -1. When you complete them, power on the switch. At the setup prompt, do nothing: The switch
begins the initial configuration as described in the “Initial Configuration” section on page4-5. When the
full configuration file is loaded on your switch, you need to do nothing else.
Table4-1 Prerequisites for Enabling Automatic Configuration
Device Required Configuration
Access switch Factory default (no configuration file)
Distribution switch •IP helper address
•Enable DHCP relay agent
•IP routing (if used as default gateway)