Startup Process

Figure 1 shows how SZTP is started.

Figure 1 SZTP startup process

The startup process of SZTP involves the following steps:

Device startup after power-on

After the device is powered on, it starts with the configuration file if one is available. If no configuration file is available, the device checks whether it has been pre-configured. If the device has been pre-configured, it runs the pre-configuration script and then starts the plug and play (PNP) process.
Information obtaining through DHCP

The device broadcasts DHCP request packets through a management or Ethernet interface. After receiving a request packet, a DHCP server replies with a DHCP reply packet. The device starts the SZTPv4 process if SZTP is enabled and the DHCP reply packet contains Option 143. Otherwise, the device starts the ZTP process if ZTP is enabled.

If SZTP is enabled and Option 143 can be parsed (even if it contains incorrect information such as an invalid IP address), only the SZTPv4 process is performed regardless of whether other options are present.
Device restart

After successfully executing the SZTP or ZTP process, the device will be restarted. If the SZTP or ZTP process fails, the device will start PNP again.