Power-Up Phase; Usb Discovery Phase; Dhcp Discovery Phase - Cisco Nexus 5500 Series Configuration Manual

Using PowerOn Auto Provisioning

Power-Up Phase

When you power-up a switch for the first time, it loads the software image installed at manufacturing and
tries to find a configuration file to apply after the switch boots. When no configuration file is found, POAP
mode starts.
During startup, a prompt appears asking if you want to abort POAP and continue with normal setup. You can
choose to exit or continue with POAP.
No user intervention is required for POAP to continue. The prompt that asks if you want to abort POAP
Note
remains available until the POAP process is complete.
If you exit POAP mode, you enter the normal interactive setup script. If you continue in POAP mode, all the
front-panel interfaces are set up in Layer 2 mode, which ensures that the device does not participate in any
Layer 2 forwarding.

USB Discovery Phase

When POAP starts, the process searches the root directory of all accessible USB devices for the POAP
configuration script file (either the Python script file, poap_script.py, or the Tcl script file, poap_script.tcl),
configuration files, and system and kickstart images.
If the configuration script file is found on a USB device, POAP begins running the configuration script. If the
configuration script file is not found on the USB device, POAP executes DHCP discovery. (When failures
occur, the POAP process alternates between USB discovery and DHCP discovery, until POAP succeeds or
you manually abort the POAP process.)
If the software image and switch configuration files specified in the configuration script are present, POAP
uses those files to install the software and configure the switch. If the software image and switch configuration
files are not on the USB device, POAP does some cleanup and starts DHCP phase from the beginning.

DHCP Discovery Phase

The switch sends out DHCP discover messages on all of the active interfaces (including the mgmt interface)
soliciting DHCP offers from the DHCP server or servers. The DHCP client on the Cisco Nexus switch uses
the switch serial number or its MAC address in the client-identifier option to identify itself to the DHCP
server. The DHCP server can use this identifier to send information, such as the IP address and script file
name, back to the DHCP client.
POAP requires a minimum DHCP lease period of 3600 seconds (1 hour). POAP checks the DHCP lease
period. If the DHCP lease period is set to less than 3600 seconds (1 hour), POAP does not complete DHCP
negotiation.
The DHCP discover message also mandates some of the options and solicits these options from the DHCP
server after receiving the DHCP OFFER from the DHCP server.
• Option 66 ( TFTP server name) or Option 150 (TFTP server address)—The DHCP server relays the
TFTP server name or TFTP server address to the DHCP client. The DHCP client uses this information
to contact the TFTP server to obtain the script file.
• IP address
OL-30890-01
Cisco Nexus 5500 Series NX-OS Fundamentals Configuration Guide, Release 7.x
POAP Process
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