PowerOn Auto Provisioning (POAP) automates the process of upgrading software images and installing configuration files on Cisco Nexus switches that are being deployed in the network for the first time.
When a Cisco Nexus Series switch with the POAP feature boots and does not find the startup configuration, the switch enters POAP mode, locates a DHCP server, and bootstraps itself with its interface IP address, gateway, and DNS server IP addresses. The switch also obtains the IP address of a TFTP server or the URL of an HTTP server and downloads a configuration script that enables the switch to download and install the appropriate software image and configuration file.
If a universal serial bus (USB) device that contains the required installation files is not available, POAP requires many services as shown in Figure 6-3. The network infrastructure requirements are as follows:
A DHCP server to bootstrap the interface IP address, gateway address, and Domain Name System (DNS) server
A TFTP server that contains the configuration script used to automate the software image installation and configuration process
One or more servers that contain the desired software images and configuration files
Figure 6-3 POAP Network Infrastructure
The reference script supplied by Cisco supports the following functionality:
Retrieves the switch-specific identifier—for example, the serial number.
Downloads the software image (system and kickstart images) if the files do not already exist on the switch. The software image is installed on the switch and is used at the next reboot.
Schedules the downloaded configuration to be applied at the next switch reboot.
Stores the configuration as the startup configuration.
Cisco offers sample configuration scripts that were developed using the Python programming language and Tool command language (Tcl). You can customize one of these scripts to meet the requirements of your network environment.
The POAP process has the following phases:
1. Power up
2. USB discovery
3. DHCP discovery
4. Script execution
5. Post-installation reload
Within these phases, other process and decision points occur. Figure 6-4 shows a flow diagram of the POAP process.
