Dhcp-Based Autoconfiguration And Image Update; Restrictions For Dhcp-Based Autoconfiguration; Dhcp Autoconfiguration - Cisco Catalyst 9500 Manual

Performing Device Setup Configuration
The DHCP server sends the client a DHCPNAK denial broadcast message, which means that the offered
configuration parameters have not been assigned, that an error has occurred during the negotiation of the
parameters, or that the client has been slow in responding to the DHCPOFFER message (the DHCP server
assigned the parameters to another client).
A DHCP client might receive offers from multiple DHCP or BOOTP servers and can accept any of the offers;
however, the client usually accepts the first offer it receives. The offer from the DHCP server is not a guarantee
that the IP address is allocated to the client; however, the server usually reserves the address until the client
has had a chance to formally request the address. If the device accepts replies from a BOOTP server and
configures itself, the device broadcasts, instead of unicasts, TFTP requests to obtain the device configuration
file.
The DHCP hostname option allows a group of devices to obtain hostnames and a standard configuration from
the central management DHCP server. A client (device) includes in its DCHPDISCOVER message an option
12 field used to request a hostname and other configuration parameters from the DHCP server. The configuration
files on all clients are identical except for their DHCP-obtained hostnames.

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 devices in a network. Simultaneous image and configuration
upgrade for all switches in the network helps ensure that each new device 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.

Restrictions for DHCP-Based Autoconfiguration

• The DHCP-based autoconfiguration with a saved configuration process stops if there is not at least one
• Unless you configure a timeout, the DHCP-based autoconfiguration with a saved configuration feature
• The auto-install process stops if a configuration file cannot be downloaded or if the configuration file is
• The configuration file that is downloaded from TFTP is merged with the existing configuration in the

DHCP Autoconfiguration

DHCP autoconfiguration downloads a configuration file to one or more devices in your network from a DHCP
server. The downloaded configuration file becomes the running configuration of the device. It does not over
write the bootup configuration saved in the flash, until you reload the device.
Layer 3 interface in an up state without an assigned IP address in the network.
tries indefinitely to download an IP address.
corrupted.
running configuration but is not saved in the NVRAM unless you enter the write memory or
copy running-configuration startup-configuration privileged EXEC command. If the downloaded
configuration is saved to the startup configuration, the feature is not triggered during subsequent system
restarts.
System Management Configuration Guide, Cisco IOS XE Fuji 16.8.x (Catalyst 9500 Switches)
DHCP-Based Autoconfiguration and Image Update
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