DHCP Discovery
After entering ZTP mode, the switch sends a DHCP discovery message on its management interface, requesting DHCP offers from the DHCP servers present on the network. The DHCP server replies with a DHCP offer message. When the switch receives the DHCP offer message, it will look for following information in the offer:
An interface IPv4 address
A gateway IPv4 address
A TFTP or HTTP server IP address (using option 66)
Boot file name (using option 67)
The switch completes the DHCP negotiation process (request and acknowledgement) with the DHCP server, which assigns the switch with an IPv4 management address. The switch then uses the acquired TFTP or HTTP server IP address to contact that server to get the boot file, The option 67 contains the complete file path of the boot file on the remote server. The switch then downloads the boot file.
If no DHCP servers reply is received after DHCP discovery message or if the DHCP offer does not meets the ZTP requirements, the switch won't be able to complete the DHCP negotiation and the switch exits ZTP mode and continues the normal boot process.
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