Cisco Catalyst 2960 Software Configuration Manual page 89

Chapter 3 Assigning the Switch IP Address and Default Gateway
Understanding DHCP-based Autoconfiguration and Image Update
You can use the DHCP image upgrade features to configure a DHCP server to download both a new
image and a new configuration file to one or more switches in a network. This helps ensure that each
new switch added to a network receives the same image and configuration.
There are two types of DHCP image upgrades: DHCP autoconfiguration and DHCP auto-image update.
DHCP Autoconfiguration
DHCP autoconfiguration downloads a configuration file to one or more switches in your network from
a DHCP server. The downloaded configuration file becomes the running configuration of the switch. It
does not over write the bootup configuration saved in the flash, until you reload the switch.
DHCP Auto-Image Update
You can use DHCP auto-image upgrade with DHCP autoconfiguration to download both a configuration
and a new image to one or more switches in your network. The switch (or switches) downloading the
new configuration and the new image can be blank (or only have a default factory configuration loaded).
If the new configuration is downloaded to a switch that already has a configuration, the downloaded
configuration is appended to the configuration file stored on the switch. (Any existing configuration is
not overwritten by the downloaded one.)
Note To enable a DHCP auto-image update on the switch, the TFTP server where the image and configuration
files are located must be configured with the correct option 67 (the configuration filename), option 66
(the DHCP server hostname) option 150 (the TFTP server address), and option 125 (description of the
file) settings.
For procedures to configure the switch as a DHCP server, see the
Autoconfiguration" section on page 3-6
Services" section of the
After you install the switch in your network, the auto-image update feature starts. The downloaded
configuration file is saved in the running configuration of the switch, and the new image is downloaded
and installed on the switch. When you reboot the switch, the configuration is stored in the saved
configuration on the switch.
Limitations and Restrictions
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OL-26520-01
Cisco IOS IP Configuration Guide, Release
The DHCP-based autoconfiguration with a saved configuration process stops if there is not at least
one Layer 3 interface in an up state without an assigned IP address in the network.
Unless you configure a timeout, the DHCP-based autoconfiguration with a saved configuration
feature tries indefinitely to download an IP address.
The auto-install process stops if a configuration file cannot be downloaded or it the configuration
file is corrupted.
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
"Configuring DHCP-Based
and the "Configuring DHCP" section of the "IP addressing and
Assigning Switch Information
12.2.
3-5